Well, I have to admit that I am into shooters (perfect for relaxing, which for me is the motivation of playing a game). I recently rediscovered Hybris. Quite an oldie (1988 by Discovery software), but I'd say one of the best shooters ever made. Cool graphics, great playability, awesome demoscene style music and massive destruction... :-D
Any other recommended shooters? (I know R-Type and the like, but I think I prefer V-scrolling.)