When CoX went dark, the ATs I found myself missing the most were the Kheldians as the lore behind them had so much potential, yet their implementation felt squandered. I'm a big fan of Venom and Spawn so Kheldians felt a bit like that with a splash of the GLC thrown into the pit for seasoning.
Otherwise during the Live era, I got a deranged satisfaction tasting the salt from the tears of pvpers that tried to kill my pvp team in vain. I mained a pvp empath and I probably am a little messed up in the head from it, like a person who willingly becomes a goalie in hockey.
Now a days, for PVE I actually enjoy my random integer generator to give me an AT, and my primary/secondary/epic pools. I only get to choose the normal power pools and then I have fun making a competitive toon out of chaos.