Believe it or not, the 7 of Cups - I don't find it pleasant, with that swampy slimy bilious-green imagery, but it challenges me....it even causes an actual physical reaction. Namely, that I start feeling nauseous...but I don't think that's necessarily a bad thing.
There's a Van Gogh painting, "The Night Cafe," that gives me a similar feeling - dizzy and nauseous - but I love it. I used to stand in front of it in the art gallery, examining it, feeling its power, till I wanted to throw up. (So maybe I'm just wired a little strangely when it comes to unsettling art, lol.)
Anything that affects me so viscerally has a lot of power, and gives me a lot to think about. And almost no other Tarot card can do that to me.