I bought Duke Nukem Forever on release knowing full well what it was, no regret. I actually like the kinda bad games and buy them willingly and they're often the games I finish. One time I bought a bad game(Matt Hazard for the 360) and accidentally got a better bad game(Earth Defense Force for 360) by mistake, so I bought Matt Hazard again, knowing I had a second chance to rethink the situation. I regret nothing, I'm a gaming garbage picker at heart, let me see what's in that trash.
Most shameful would probably be Tobal No.1 for the PS1, just for the Final Fantasy 7 demo... that wasn't included in the European version... Part of me knew that but I stood around for hours in a store that sold imports and weird pirated games, waiting for their delivery and then bought it anyway. We actually got into playing that game, it's neat fighting game and 60fps plus some fluid animation goes a long way, then a friend borrowed it which ended with someone getting stabbed. Anyway, I actually ended up buying another copy.