Oh Loki! <3 <3 <3 Yes... Oh yes... Especially with his love of illusions. I'd love to see his bag of 'tricks' as Thor called them. xD
I discussed this with someone here the other day, one thing that just caught my eye in X-men First Class was Emma's Frost's ability to make someone do and believe they're doing acts (in the film's case having sex) while she was sat somewhere else in the room completely, sat looking utterly bored. Personally I'd love to see Xavior use this skill as ler, but I'm sure she'd definitely thrill in making some poor helpless victim squirm, beg, laugh, and plead while she's on the other side fo the room, laughing...
There's also Mystique, who always has that wicked grin on her face.... Perhaps in some iron grips tightened especially by Magneto... No I did not sigh dreamily. *innocent eyes* I'm surprised no one has mentioned Mr. Sinister as well. Given his love for expirements in the name of well science. *blush*
Harley Quinn and Poison Ivy definitely (those two alone let alone together make a frightful team *shudders*). Cheetah too, given that in the original comics by Aprhodite's Law if Diana (Wonder Woman) was bound she was powerless (literally) Cheetah would certainly RELISH torturing the strong amazon as a captive with those sharp nails...
From Disney Hades from Hercules would be a good ler I'm sure. Those dark tendrils of his sent shivers down my spine, not to mention those pointed fingers. Maleficent also has such fantastically sharp nails... Maybe torturing a sleeping Aurora or a chained Prince Eric. Captain Hook with that sharp hook (I actually thought in the cartoon they were going to tickle Tiger Lily with feathers or such but they didn't...), the wicked Stepmother from Cinderella, or oh the Mother from Rapunzel... Really quite a few Disney villains would make great- well better tormentors. xD
Bella Lestrange seems much too into pain to use something so human as tickling (especially if it meant having to touch the 'filthy Mudbloods), but maybe she'd have some House Elves do it for her. Umbridge I think would use it for interrogation though... Especially since she's very into the 'hands-on' approach. On a side note, for some reason I always pictured she was tickled by the centaurs after she was dragged off...
I know this doesn't count as a villain perhaps... But I always thought if a Hydra was set to tickle-mode instead of kill it would definitely be a terror to be stuck between all those tongues. And going into Greek Mythology, there's also Medusa who I really think would be into using tickling to get her potential victim to turn around, with those snake tongues around her head or by sneaking up behind them...