Let's see, similar to above, I had to solo the last part of a Synapse TF. One of my most favorite achievements, really. The GM ambush was the most memorable moment though: One of my teammates had come back, and I had spammed my predicament across all channels before exiting the instance which spawned the Paladin. The BIGGEST turn-out for a Paladin call-out I've ever seen had arrived to help: 50-odd heroes iirc, and he was down in seconds. On one hand, it was a bit anti-climatic, but on the other hand, it was pretty heartwarming seeing that many strangers and a few friends come to my aid =)
Made a character with the plan to not use any pool or travel powers. But it was Kin/elec (so that was cheating a bit), and then they made the fitness pool free, sooo nothing hard about that.
I did low-level Exploration badge runs, and got pretty good at it. Cheesed me off to no end when someone hosted a lowbie badge-hunting race and I didn't even win! (I think i was 2nd or third, but only because I was too proud to try and die and hosp it to get across IP).
Was playing on my Mind/Kin/Psi in the clockwork dimension map with a full team; The Clockwork King made short work of the invuln and fire tanks, so I took over. Between high psi resists, confusing CKs minions and using my healing powers, I successfully tanked an AV with my controller. In fact, I was initially just buying my team time to escape, but I kinda got "scrapper locked" into staying in combat. I eventually panned my camera around and saw the WHOLE team just standing on a nearby garbage pile, just watching me. I had to yell at them and come help: not because I was in any danger of dying, but because I couldn't quite out DPS the AV's regen, even with a regen debuff being spammed on him every 4 seconds. But yeah, that was as ridiculous as it was epic... for me, at least.
After my Mind/Kin had hit 50, but before Inventions or Incarnates, I spent most of my time with her TKing enemies into police drones, or seeing how high up I could levitate lvl 1s in AP.
I once trolled an MM in Recluse's Victory by using Repel to scatter his henchmen across the map. He got wise and dismissed them, but I kept his giant spider-bot and rolled it around the map. Whenever he would find me, I would yell "MINE!" and run off with it again.
I'm sure there's more, but that's all I can think of at the moment =)