Beating Turrican 2 for the first time on the Miggy and listening to the great end tune
Finally finding out that wearing a chain mail and having an armor class of 2 is actually better than running around naked with an armor class of 10 in Champions of Krynn
Beating Doom II on UV for the first time (a lot of cursing involved
Getting through Day of the Tentacle with only one hint by a friend (on the phone, at 1:30 AM, luckily I survied that
Second the Morrowind moment
Also great to see, that when you 'finish' the game you can just go on playing it.