By far my favorite troll-like being is Kokopelli, the hump-backed flute-playing trickster god of the Hopi and the Anasazi. Like many of his ilk, he is a bringer and protector of fertilty, a bringer of spring rains (and chaser-away of winter), as well as a god of music. He is mischievous, but not truly evil -- and who wants their supernatural creatures tame and docile all the time anyway?!
Another favorite, this one truly of the tug-at-heartstrings kind, is Dobby, the much-abused but finally liberated house elf from the Harry Potter books. I mean, seriously, how could anyone not love him?
Other favorite supernatural beings (not troll-like):
* Elves and fairies (of all incarnations) (Yes, I know, technically Dobby is an elf, too, but he looks much more like a troll or a gnome to me.)
* and of course, dragons!
(Task: Trolls, gnomes, dwarves and similar beings (some evil, some less so, almost all of them mischievous) are a staple of Scandinavian mythology and folklore, as well as other folklores and mythologies around the world and, of course, fantasy and speculative fiction. Who is your favorite such creature and why? (No matter whether mythological, fictional or from whatever other source.))