Inside pen in F4.
Remove the Troll from the bridge to the Gnome Island.
+5 show carrot to Goat, +4 have goat remove Troll, -5 have Goat escape from pen.
Don't open the goat pen and leave the screen—the goat will escape and you won't be able to get him back.
Although the goat isn't really an item you can keep, he is very useful because he will remove the annoying Troll from the bridge to the Gnome Island. To remove the Troll, simply walk up to one of the bridges leading to the island and let the Troll come out to demand payment. The Goat will butt him off the bridge and you will be rid of him for the rest of the game.