Already have Commander Keen.
Along with many older games including Wolfenstein, Duke Nukem, etc.
Let'* see.... I have a IBM Aptiva 166MMX I just picked up last night for $5, a Compaq Presario All-in-one I picked up last night for $5, a ThinkPad 760c (Pentium 120), a ThinkPad 760XD (Pentium MMX 166), a IBM desktop in the closet, I think its a 166MMX, 2 old *** IBMs in the basement, iPaq H3835, and my Daily ones, a Quicksilver 2002 G4 and a ThinkPad 570E PIII 500. I know I have more, I just don't feel like listing it.