[Rumil]

How about the Troll in 'Perry the Winkle' from the Tales if Tom Bombadil? He seemed a fairly cheery type, the flipside of Bert et al. Also there's the Troll in one of Sam's songs that Tom regretted kicking.

We do get to se a few trolls in the Silmarillion (seventy that had a bad day when they tried to capture Hurin!!), but not in much detail.