Alien/Predator... NOt that I want to see them crossed over greatly mind you, but a comic/story would be neat I think... IN particular though, Alien. It just fits... A guy years ago made an AWESOME level for Jedi Knight that was indeed an Alien/Star Wars crossover.
The story's premise, the level design, and the game dynamics were excellent. He made a new alien character designed from the floor up (coded, drawn, and skinned by himself). The game's engine was easily modified... For someone who can do that stuff anyway.
The premise was this:
Imperial Installation on remote moon is doing supposed "biogenetic" testing. New weapons to implement in its conquest of the galaxy. Money's funneled there, but nothing ever comes out of the planet's base... The Alliance sends one of its infiltrator's, which are the elite of their Spec. Forces units, into the base to obtain data on what's going on. Kyle Katarn's a Merc Infiltrator, there's teams of them (kinda like Rep. Commandoes, more intigrated into the military structure), and this guy was like their Snake Eyes more or less.
He gets in, and upon obtaining some material to bring back to base, he breaks what basically is containing these cages where testing is going on... Inconsequential, but when he gets out of the lab, the base has gone to ****... Aliens running around... Stormtroopers getting mauled... Imperial scientists running like morons. It's really quite great, and the game play is probably in the top 3 best modded levels for Jedi Knight, which used to have an extensive community, so that says a lot I think.
The basic premise from there is escape, but the base has taken severe damage from the alien rampage... Sometimes Stormtroopers help, sometimes they attack, and other times they just run around as scared as everyone else. You make your way out of the base and the report goes back to wipe the base out at all costs to prevent whatever "weapon" they were trying to create with the Aliens themselves.
Pretty neat... And every reason I decided to buy the Alien/Predator figures from Hot Toys. As we speak there's Preds walking my Cantina and Jabba's Palace set-ups, and they fit in quite well... Aliens are currently tearing apart a Stormtrooper squad on a shelf becuase I haven't found a good home for them yet. They fit in so well though, it's funny.