I suggest Unreal Tournament 2: The Liandri Conflict and Oddworld: Stranger's Wrath, if you don't have them.
Also, Splinter Cell: Chaos Theory.
I really can't describe UT2 (probably gonna try to review it soon, but I kinda suck at the game now), so I suggest checking out some video reviews or something. Oddworld is a combination 3rd-person platformer and FPS that works WAY better than you'd think it would. It's a great game.
Chaos Theory is arguably the best Splinter Cell game ever and possibly even the best stealth game ever, although I'd argue that Hitman: Blood Money is a better game (but some would say that BM really isn't much of a "stealth" game.)
All of these games can be had together for probably less than $15 American, if you shop secondhand. $20 at the most.