What single player games do you enjoy replaying?

[VAMatt]

I replayed platformers often in the 80s and 90s. But, in the 21st century, the only game that I've replayed multiple times is Halo:CE. It is probably the most significant game to me personally. So, I like to revisit it from time to time. Other than that, I just want to play new stuff, rather than games that I've already played.