Wotlk UH dk: original chains of ice, good self sustain, great kiting and peeling, and good damage without cds. I liked how it was a dot spec, and I really hate the scuffed bm hunter/demo imitation that it has become.
Wod Fdk: mostly same reasons as you mentioned. Also importantly because it did damage outside of cds. And it was fun to be able to spam purge with that one removed frost rune spell, I don’t remember the name.
Classic+tbc SP: It wasn’t the best, but it was just very fun and unique. That’s all I played back then, so it’s probably nostalgia.
For me, it is MoP Enhancement Shaman.
TBC Shadow.
WotLK Death Knight and Arms Warrior with BLADESTORMMM
WotLK Retribution Paladin had a pretty cool talent tree compared to how bad it was in Vanilla and TBC.