In Ace Combat 04/5/Zero, I always unlock Ace Difficulty with a bit of trouble on Expert. Once I get to Ace, though, it all goes away. All of a sudden, I dogfight and can take down every enemy without taking any damage. I will pursue enemy squadrons to the last man, and I can destroy every target on the map. Where is your god now, Belka? What good are your superweapons, Erusea? I am become death, destroyer of worlds. I am the alpha and the omega, the beginning and the end.
Then there's Oblivion. Once I powered through the Fighter's Guild and Mage's Guild quests, Mankar Camoran had no chance against me. I raised my trusty enchanted longsword and there went his face. I also made a character and powered through the Dark Brotherhood quests. I could sneak into the Imperial Legion headquarters and kill them off one by one without being noticed. The Thieve's Guild quest where you steal the Elder Scroll? I walked straight in and straight back out. 100% Chameleon, maximum sneak skill.
Another was Rainbow Six: Vegas 2. Once I got my chosen weapons, I could sneak about and kill every enemy player, both AI and person. In Terrorist Hunt mode, I'd do it Realistic with maximum enemies.
Incidentally, these games are the only ones I am truly very good at. When it comes to other games, I'm kind of meh-ish.