Aliens vs Predator makes incredible use of rain in the DLC survival map called Tempest. I think it's the only map in the whole damn game to feature any form of abnormal weather whatsoever. But as you progress through the waves of aliens as a colonial marine, the rain outside the compound area you're defending gets heavier to the point where in the later stages you can barely see a few feet out, let alone an approaching alien until 10 of them are right on top of you. Very gritty and atmospheric map. I wouldn't say it's worth the full price of the game, but it's certainly one of its stronger points.