I've had plenty of characters I've enjoyed, but some do shine a bit brighter in my memory than others. On MUs, I suppose these three stand out the most:
Faolan O'Rourke, a rundown and lazy 'old hand' in The Reach's Police Department. I loved the Law Sphere and its sense of community, and the small beat cop moments that some pretty great storytellers wove. And of course the people were (if not universally) pretty great. At least the ones I had anything to do with. He nearly had a heart attack getting shot at, fell into a massive depression after being dragged into a ghost story (he was willfully ignorant of the greater world of darkness), and had a chance to educate some new grunts from the academy in the best ways of avoiding a) working too much, b) where to get the best food for extended lunch breaks, c) how to get other people to do your paperwork and d) survive!
David Wright-Phillips Austere, of RfK. I find it hard to count the brilliant moments of fun on that game, even if it had its share of great frustrations as well. He was only really supposed to be a Carthian to look after his ward, while trying to convert her into proper Circleness, but for various reasons he ended up deep in the Carthian conspiracies. I'm still a bit sad that the first version died before he had a chance to seize the reigns of Prince, since I'd have loved to see the fallout of all the double dealing scheming he'd been up to to secure it. Shoutout to @Ganymede 's Cai, who was delightful, and @Caryatid 's Nora, and @mietze 's cannibal ghoul (the things you can bond over). The dynamic he had with Baptiste was pretty great, too. Both working for the cause, but with all the tension of ambitions vampires with opposing religious views. They orchestrated the ascensions of the Movement and the overthrow of the Invictus. He always intended to make Baptiste pay for making David beg forgiveness for insulting Phineas, (Phineas' condition for being Baptiste's Sheriff and supporting his Praxis), though. No, neither being made Seneschal or the boon covered the burning humiliation of that moment, not even by a long shot!
Alphard Pollux Black, of Witchcraft and Wizardry. I pretty much made him just for a lark. He was obnoxious, and terrible, and quite easily manipulated by preying on his various bigotries or oversized ego. Both happened quite a lot, which I greatly enjoyed. He was also the butt end of many a joke, and that was sort of the point, too. I remember best Ria, and Medusa, Andromena, Douglas and Julian, and all that Harry Potter hijinxing.
With honorable mentions to brutish Victus Thrax, the always cowardly Corrigan (Pete, you should've listened when he said he was going to run away. RIP, buddy), the always dependable Ser Harold Charlton, and vamp-hater Recket with his endless supplies of fireballs.