I game quite a bit, so I have a PC.
Yes, I know I can play ~12% of games on my Mac, but that's just not quite satisfactory for a gamer like me. 😛
12" G4 iBook - mobile web & email
G4 Graphite PM - always-on video transcoding
3GHz PC - workstation & gaming system, due for upgrade by Spore release 😀
1GHz PC - RAID fileserver, print server, & game server
PS: Yes, I know I could BootCamp my PC games if I bought a new MacIntel, and maybe someday I will. However, it seems like a waste of money when I can get MacPro gaming performance for a fraction of the price by building my own Windows box.