Worst/Best: Final Fantasy 7. I bought it for the PC and was playing it and it crashed.
A lot.
I couldn't figure out what was wrong. I tried everything from new graphics card to new RAM... I limped through that game in low res for several weeks, saving every possible second. I couldn't even get through one of the boss battles at Red 13's village because I'd crash halfway through the battle. There was much screaming and cursing.
Finally one of my friend suggested taking the cover off my computer. I figured "Why not? I've tried everything else" and did that.
Three hours later I was still playing, narry a crash in sight even after cranking up the graphics display to max quality.
Life was good. Life was VERY good then. :D
One additional memory, neither good nor bad, just odd: I was fighting Ruby Weapon for the first time. I didn't know it was invulnerable until you were down to one party member. I did know what Lucky Sevens were and had one of my characters (Vincent) in Lucky Seven Mode.
The battle starts, Vincent goes first, steps forward, shoots, does 7777 points of damage (which means nothing because Ruby's Invulnerable), steps back, and because his target isn't dead, he steps forward again, shoots, steps back...
Repeat. A lot. It was classic "unstopable force vs immobile object as the carera did a continuous 360 pan. I thought I broke the game, so naturally I called my best friend and told him what happened. :D
Somewhere after I don't know how many repeptitions, Vincent finally stopped and I promptly got my butt handed to me by Ruby Weapon, but that was okay - I beat it later.