I mentioned this on the First Light thread, but hopefully thet will be going away soon - to be replaced with the First Light Release Party topic.
You can try out the rules here: http://fantasyflightgames.com/doom.html
The squares in the game are 1" so you could use just about any of the WW sets with it. (In this case being able to fit the figure in the square is more important than how big the square is.) Can't you imagine a Doom/Skull Cove set, for an attack on Gilligan's Island? (Skipper!)
It looks to be closer to Space Crusade than to Space Hulk, but does come with 2D floor tiles. And a bunch of unpainted plastic minis. A bit more about the game here: http://www.enworld.org/forums/showthread.php?t=111956
I gather that it can be found discounted for about $35 US. *EDIT* For the full game, the rules as I mentioned are free.
The Auld Grump, now if they come out with Halflife...