Goats

Goats are well known for their total dislike of trolls.

Background
There is a tale of three billy goats on their way to pasture. They had to cross a bridge to get there, and a nasty troll lived under it. Now some trolls like to east the flesh of humans, but all of them delight in devouring goats. As the first goat went across, the troll went for it; but the clever beast convinced the troll to wait for his bigger brother, as he would make a larger meal. The troll waited and rushed the second goat, who too convinced the troll that there was a yet larger goat still to come. When the largest of the billy goats arrived, he rushed the troll, butted it off the bridge, and killed it.

It is said that goats will eat almost anything; if one show one a carrot and it follows him anywhere. It has been said that if one shows a goat an old shoe or a tin it follows him anywhere.