This is a tough one... I've played so many games that I can't really think of anything other than my 14-kill round of CS (30 man server, 15 per team) and beating Goldeneye on 007 difficulty (not really that hard, just time-consuming).

for me it has be beating sephy on kh2 with no magic, no items. level 85, full forms, ultima though. he isnt hard any more :(

I would of forgotten most of the games I have finished, over 50 easy.

i beat both frog bosses without the pause cheat. Did a number on my thumbs too.

i got gold on every track in every gran turismo...with out cheats......yup

@AnthonySam: Wow.

Actually I much prefer using the triple boomerang as opposed to the holy water on Dracula, and the Grim Reaper as well for that matter (although beating him with holy water is easier).  The first form of Dracula is fairly straightforward with practice, and the second form just boomerang him in the face over and over.  It's pretty tough to beat some places all in a row without dying obviously, though, and it's easy to slip up on level four, Frankenstein, the Grim Reaper or the clock tower.

I did not use the pause trick in Blaster Master.  I can't remember that much about it because I did it years ago and haven't picked up the game since.  The game is incredibly difficult, especially considering you have no save or password and it is a LONG game! 

Blaster Master was a blast.  True hardcore gamers who have never played this should hunt it down for NES and play this game.  Leveling up that tank/vehicle that you rode around in was innovative and fun.  And jumping out of your car to have to adventure in the larger world are, plus going into dungeons type levels was equally fun. 

There was a remake for Blaster Paster for PS1, but it was selling for $10 at Toy's R Us.  With that and the fact that I had never heard of the PS1 game, I assumed it was crap and did not bother picking it up. 

I COMPLETED SONIC THE HEDGEHOG 1 and I ended with all 3 lives intact... no continues... =O