I can remember a few:
1) Kid Kourage was a teenage Scrapper and fairly small, got on a team with missions against MALTA. Those Titans, laying dead on their sides were still taller than me. Got into one fight where there were so many of them, I had absolutely no idea what I was attacking, or even in what direction, for several minutes.
2) Shatter Rat was an Earth/FF Controller; she was way over the defensive soft cap with that combination and her pool picks. Had someone ask me to try some Architect missions he'd designed. The first couple were a little lame but the third was a tunnel crawl. We hit a cavern with a Nosferatu-esque boss which triggered a mass of ambushes at the same time. He bailed the mission, and quit the team, but I stuck it out. With Rat I was so used to having to nibble away one target at a time while ducking/containing the rest of the mob. About a half hour later, the jerk sends me a tell, laughing about how his deathtrap scenario was unbeatable right about the time I was finishing the last stack. I offered to let him rejoin the team and see for himself. He couldn't believe there was just a "punk Earth Troller" and her Stoney on the entire map.
3) The day I got an HPE-580 64-bit Windows 7 machine to replace the Dell 2300 Windows XP machine I had been playing on and it could actually handle the frame rate of a Rikki event. The old machine had been so much like being in a strobe light, with just random images and power recharge times. Sad to say, it did Rikki events best by just maximizing my zone map over the screen, so it never had to resolve the visuals for me. Oh, and then being able to game using Ultra mode instead of the lowest settings. So awesome!!!