I ♥ lemmings. It's a fun puzzle game, and it has good nostalgia value for me. I first came across the game in middleschool, where I found it on the computer lab computers. We (the lab boys) removed it from public access, chiding the person who installed it publicly...and of course, in the spirit of things, moved it to a private directory where the lab techs could play it when we so choose. :) And boy did we ever.
Now I just have to beat something like a few hundred levels (again). :)