Metal Gear Solid 3: Snake Eater
GTA San Andeas (Sp?) was good too. I remember I had paid vacation from work when they were coming out. A week by myself (well I saw some freinds too). Good times.
Manhunt had some flaws but was good overall, same for Hitman: Contracts. Contracts was a step down from the last in it's series in game controls though a step up in inovative environment interaction.
Oh yeah and I started X-Com for the first time ever and got hooked. Retro for ya.