Mega Man 2. I would try and beat every boss with just my regular weapon or refuse to use Item 2 for the block section at the end of Heat Man's stage. Also, if I felt really into it, I would beat the stupid boss from Wily's Castle 4 without doing the Start button trick.

world of warcraft classic and burning crusade

and on console crash bandocoot and mario kart 64

I would say NiGHTS into dreams. Getting continued links was hard but I managed in time to rack up huge scores :).

Fire Emblem Radiant Dawn

I have played it so much that I know exactly what to do in every situation and I never loose anyone... it's kinda sad.

For real time games, definitely Mario Kart 8. I come in 1st practically every time.

Crash Bandicoot 3 and Crash Team Racing

Symphony of the night and yugioh forbidden memories

Black Ops 1 Multiplayer. I wish Twitch had been implemented on consoles back then.

Went 117 - 2 in a match once

All without the guide.

There's no game I'd consider myself an "expert", but I absolutely love the Dead Rising games and I know every single detail, secret, and thing to do and where to collect items in the first and second entry.

ESPN International Track And Field for the PS2. When you got your score at the end, you got given a code which you put on to the Konami website. I was first in the world for about 6 months after release and out of nowhere I ended up with a years supply of Konami games, T Shirts, CD Soundtracks, everything!