Space and money makes me regret selling everything but biggest regrets:

KISS LE with Topper. Kiss is a good game, not a great one. Love the theme though. I finished everything in it before the last code update made it "easier". The fact that I'll have to pay $4K more than I sold it for means I'll never own it again.

Sweet loaded, LOADED Tron Pro.

NO REGRETS?
Dialed In LE (soulless game)
Ghostbusters LE (100% Ghostbusters, 0% fun)
Batman The Dark Knight (I'm convinced it was actually designed in the dark)