Ever since I played Rogue on IBM-PC's back in 1989 (I'd call that the original rogue, but I'm afraid of a mountain of fanboy corrections), I've always enjoyed a rogue-like. Small files that can be loaded anywhere, and can kill a boring afternoon -- always good stuff. Omega, Nethack, Moria, you name it, I've at least tried it. I'll bookmark this one for later.
If you like roguelikes, check out this site here:
{web page} It's a wiki about various roguelikes. I wouldn't call it a definitive resource -- people aren't really filling in the descriptions like other Wikis out there on the net. But it has way more entries pointing to rogue-like development sites than you'll find buy searching google.