Fast Attack:
Assault Squad: Your basic Close Combat Unit for Space Marines. They get more attacks then Tactical in Close Combat and are more mobile but sacrifice the shooting capability. You can get a Rhino or Drop Pod for free by removing Jump Packs but now you can't assault out of them on the turn you get out in any situation so it is Probably better to keep the Jump Packs. If you want to use Assault Squads your probably best taking them with Shrike or playing Blood Angels.
Vanguard Veteran Squads: The Decked out Assault Squad they can all take special close combat weapons and/or Plasma pistols. Heroic Intervention lets you assault out of Deep Striking which may sound cool but must be declared before they scatter and you lose the ability to run or shoot. that could put you well out of range of what you want to assault and a Stationary target to lots of gunfire. They are iffy at best and since random Charge Length you may not even get in when your 3-4 inches away. If your going to use them take Shrike to at least make them slightly more reliable but even then I wouldn't take them.
Land Speeder Squadron: With the Inclusion of Jink your Landspeeders are a little more Durable than they were before but with 2 Hullpoints and Armour 10 they aren't that much. Otherwise a very fast weapon platform that you can move across the board to take out key squads with its equipment. The general Consensus is the best choice would be Multi-Melta and Heavy Flamer especially if you take Vulkan. If you want to specialize in Anti-Vehicle or Anti-Infantry you can take 2 of either. The only Question I have is the Tornado Patter which I think means a Pivot Based one that is on the bottom of the Landspeeder compared to the Limited firing arc of the one up top.
Space Marine Bike Squad: Jink, Hammer of Wrath, and the Toughness Increase now working on Instant Death makes a Major buff towards all bikes. If they move they get that 5+ cover save. If they need to assault they get an Extra STR 4 hit before anyone starts swinging. and the Toughness Increase is more Beneficial to your HQ,Command Squad, and your Attack Bikes. They are still finicky and with the ability of Rapid Fire to move and fire the same distances relentless seems less useful but the bikes being able to Assault after shooting all the Bolter and Heavy weapons then getting Hammer of wrath may make them a little more adept. Taking a Captain on a Bike lets you take them as Troop Choices as long as 5 are in the squad. You will Sacrifice model count for this though and you might want to support them with Scouts or Tactical Squads. I have had no Luck as running them as my only Troop choice. They will be tougher than normal marines but have less forgiveness when you fail those one or 2 times.
Attack Bike Squad: Basically a Heavy Weapon Team of Bikes. Taking Multi-Meltas or Heavy Bolters they can be very Devastating to tanks or Infantry. They are even better now with 2 wounds and Toughness 5 Melta and Lascannons won't instant kill each of your bikes and Jink will give you a chance not to take that wound at all. Don't Assault with Attack Bikes they have a lot of Gunpower and No Worthwile Assault Capability. Hopefully if they do get assaulted the attackers die in Overwatch or are stalled long enough for you to get a good CC unit in there.
Land Speeder Storm: A scout Transport that disrupts deep strikes of the enemy army. A Must have if your doing a Scout Based army Especially with an Assault Based Scout Squad. Reducing the Enemy Squad to Leadership 2 if you manage to win combat you can wipe out the whole squad with a Sweeping Advance. Open-Topped makes it even more Fragile than a Regular Landspeeder but allowing for more gunfire and being an assault vehicle.
Scout Bike Squad: I don't see much use for them they have a lot of Gimmicky Stuff. The only good thing is they come with the ability of a Locator Beacon so you can speed them in during Infiltrate and Scout to make sure Deep Strikes land in proper positions.
Stormtalon Gunship: Its the Most Fragile Flyer in the game right now with only 2 Hullpoints but it has the firepower to make up for it. Being the Smallest Flyer you can gain cover with it easier than others and make sure it stays on the board easier. With a Twin-Linked Assault Cannon you can change its Twin-Linked Heavy Bolter for a TL Lascannon, a Typhoon missile Launcher, or Exclusive Skyhammer Missile Launcher. The Lascannon isn't worth it unless you really want to take down vehicles or other flyers but even then your probably better off with the Typhoon Missile Launcher. I would take Skyhammer Missiles on 1 if I was taking 3 to finish of a Vehicle or Flyer I already softened up with the other 2.
Heavy Support:
Devastator Squad: Your Bread and Butter all around good Choice for Heavy Support. They can be equipped with a magnitude of different weapons making them useful in most situations or you can specialize them making them Deadly to a particular target. Signum granting one with a BS of 5 for a turn can make that crucial shot almost assured. With the introduction of Flyers when Flakk Missiles come out I wouldn't be surprised to see lists running 3 Devastator Squads with 4 Missile Launchers in each.
Thunderfire Cannon: Its good now. No Longer a Glass Cannon that can be glanced and killed by Bolter Fire the Thunderfire Cannon Can Lay havoc down to Infantry like you wouldn't Believe. I have 1 and in 6th edition its always made its points back so far. Getting a 75 Point Techmarine in the Bundle for 100 points makes it a steal as you bolster defenses and put another squad like Scout Snipers in to support you.
Land Raiders in general: Armor 14 make them very Durable Transport with 4 Hullpoints but Unfortunately they can be Glanced to death very Easily by a lot of Armies now. If you keep them alive they will keep the battle in your favor. They Die quickly you lost anywhere from 1/4 to 1/8 of your army. Avoid them in Low Point Games and in High Point Games your still gambling as they probably have an answer for them.
Predator: Cheap at 60 points they can crack open transports quite well. With about a doubling of the Price they can become a Deadly machine of death towards Vehicles or Infantry. I haven't quite cracked what to do with them atm I think if you take them take 3 of them and aim 2 of them for Vehicles and one for Infantry.
Whirlwind: If your thinking about taking a whirlwind your better off with a Thunderfire Cannon. They lack the Power to really Work on Vehicles and lack the Numbers to work on Infantry. They also have that deadzone of 12" around them you can't do anything about. With Armour 11 they are going to be popped very easily and will probably never get the points back.
Vindicator: I am going to get chewed out for this one. I think they are worth taking as long as you take more than 1. STR 10 ap 2 Large Blast at 24" will Decimate Vehicles. Decimate Infantry. Kill off Lower Toughness HQs and Characters. Devastate Terminatours. and the Like. Armour 13 means that a 6 on a Lascannon will pen a 5 will glance. Being Glanced now won't severely cripple the vindicator with a Stunned or Shaken or even a weapon Destroyed or Immobilised. They still are limited in Range but with a movement of 18 in one Turn now you can get them in a nice spot turn 1 and start firing round 2 no problem and possibly with 25% hull coverage to give them a nice 4+ cover save. I think they improved quite a bit from 5th edition but that has yet to be seen.
Sample Army List:
This is a Very Basic Army at 1500 points I am putting together. The purpose of this list is a Very Solid answer to everything you may find. I am not saying this list is going to destroy everything you face but you won't feel overwhelmed and has some I feel very solid Choices.
HQ:
Vulkan He'Stan (190 Points)
Troops:
Tactical Squad 7 Bolter Marines, Multi-Melta Marine, Flamer Marine, Sergeant with Combi-Melta, Rhino Transport (215 Points)
Tactical Squad 7 Bolter Marines, Multi-Melta Marine, Flamer Marine, Sergeant with Combi-Melta, Rhino Transport (215 Points)
Tactical Squad 7 Bolter Marines, Multi-Melta Marine, Melta Marine, Sergeant with Combi-Melta, Rhino Transport (220 Points)
Heavy Support:
Thunderfire Cannon (100 Points)
Thunderfire Cannon (100 Points)
Devastator Squad 4 Missile Launcher Marines, Sergeant (150 Points)
Fast Attack:
Stormtalon Gunship with Typhoon Missile Launcher (155 Points)
Stormtalon Gunship with Typhoon Missile Launcher (155 Points)
Total Point Cost: 1500 Points
The goal with this list is not to heavily focus on one type of unit but have an answer for everything. You will be putting all your Tactical Marines in Combat Squads before deployment and in 6th both can be inside the same transport. You will do this for both your squads with Flamers but the Squad with Melta you will keep 5 Bolter Marines back sitting on an Objective or protecting one of your Heavy Support Choices. The Remaining Marines your Sergeant, The Melta Marine, Multi-melta Marine, and 2 Bolter Marines will deploy in the Rhino with Vulkan He'stan attached to them. Your Thunderfire Cannons will Bolster 2 different terrains in your deployment zone and deploy into them. Your Devastator squad will deploy along with one of the Thunderfire Cannons in terrain whichever one has a better vantage point and/or better cover save after being bolstered. Your Stormtalons will stay in reserve and be deployed when they come in.
Depending on the Mission Type and type of Deployment you will change what you want to do during deployment but this is the basic idea. Everything in your Army has weapons to use against Infantry, Vehicles, Tanks, and Elite Squads. Tactical Marines will have Melta and Flamer to assure victory over infantry as well as Grenades and Melta for Vehicles. Your Devastator Squad will have Different Missiles for both Infantry,Vehicles, and Tanks. Your Thunderfire Cannons have Shells to Devastate Infantry in the Open, In Cover, and slow down units movement. Your Stormtalons will Be able to hopefully deal with other Flyers and if they don't have any the will devastate Vehicles and Infantry alike while being terribly difficult to shoot down.
I stayed away from Elites mainly cause of their focus on one Task. Assault Terminatours won't do much outside of CC and they will be slow to make it across the field unless I give them a Landraider which costs another 240 points for the cheapest one. Deep striking Assault Terminatours in leaves them vulnerable to shooting for a turn and usually your opponent will focus everything on them to make sure the don't survive. Regular Terminatours are the same issue they have Stormbolters but they need to walk across leaving them open to Gunfire and with an Invulnerable of 5+ means they will be eaten alive by Lascannons, Plasma, and Melta. With Deepstriking you will get a round of shooting in which will hopefully allow you to take out what will kill them but if you don't they will die. Dreadnoughts are Great but I just didn't feel a place to fit them in this list unless you drop the flyers but unfortunately Flyers will be needed in a lot of 6th edition games to deal with other Flyers until Flakk Missiles.
I Hope the Army list is useful and I encourage others to post their 6th Edition Space Marine lists and talk about your ideas.