Triarch Stalker (Walker)
Tomb Blade (Jetbike)
Doom Scythe (Skimmer/Bomber)
Night Scythe (Transport)
Canoptek Wraiths (jump infantry) seems GW USED to make a similar Necron unit called Wraiths that is now OOP
Canoptek Spyder (Mon. Creature) Forgeworld makes something SIMILIAR, but still different and still expensive
Maybe i'm spoiled because my grey knights have almost everything in their codex represented by a model. I haven't been around 40k long enough to see past practices with other codexes.
Keep in mind that lately GW has been releasing models for the new armies in waves.
It remains to be seen if we will be getting wave two at the end of the month or not. Usually they release the Battleforce and another model or few two - four weeks after the initial release.
I would suspect that Necrons follow the Dark Eldar pattern more closely than Tyranids. GW has definitely changed things up considerably since then and now.
Grey Knights saw most of their product line very early because there were very few models involved.
The fact that tomb spyders, scarabs, and wraiths have been flat out removed from the GW site is more evidence that we're going to see them put out new kits. Just a matter of time...