It's a different question from, say, who you'd like to have sex with, isn't it (even though there's overlap). Despite my hopeless crush on Chloe Sevigny I don't picture her tickling me.
When this question has come up before my answer was either Maggie Gyllenhaal (because I think she'd be so playful) or Shannen Doherty (because I think she'd be completely mean and cruel).
But after catching ten minutes of The View on Monday and hearing them talk about tickling, I need to add my old guilty crush Elisabeth Hasselbeck. She's dumb and no cuter than any of a hundred young moms at a mall or a public library in Milwaukee or Indianapolis, but she is cute, and at heart I think she's probably mean too, and so capable of cruelty.
In fact I'm currently having a vision of Hasselbeck and her old colleague Meredith Viera--Hasselbeck with her blankly mischievous smile, Viera with her well-muscled forearms--tickling me from either side, and while I've never thought of having sex with either of them, it's oddly provocative.