Everyone I know pronounces Troll to rhyme with mole, but I've always pronounced it to rhyme with moll (with the 'o' as in bottle (and i know if you're from west-coast Scotland they're the same sound, but think World-Service and bear with me)).
I've no idea where i got this, and i've been this way as long as i can remember.
How do you pronounce it?
Is it a regional thing?