For me, "PC gaming" means using the Arrow Keys, Ctrl, Alt, Shift, and Spacebar. Old platformers (Jill of the Jungle, Jazz Jackrabbit, Commander Keen) or dungeon crawlers (Wizardry, Cyberdogs), early FPSs (Doom, Wolfenstein, Heretic, Hexen), or just random shit that I found (Raptor: Call of the Shadow, Skyroads, Scorched Earth, etc).
If I have to use a mouse in conjunction with other things, I lose interest. I'm not sure why.