The hitman series is definitely what you want then. Hitman 2 is pretty dark and really fun with a ton of diverse levels and great freedom while not being so ridiculously stealth oriented like splinter cell. you can do steal, go in killing everything, set off little traps and well thought out plans etc. The first game had really bad graphics and not a lot of great gameplay mechanics and the 3rd one which went back and did some of the old stuff again i remember not liking so Hitman 2 is probably your best bet (especially replay value, I spent many hours going through the levels that take you through the office/skyscraper just shooting the fuck out of everyone with an automatic shotgun, fucking awesome).