I like my gold even though shops are not emplemented in the game yet. I try to avoid Leprechauns as much as possible since they will always take some of your hard-earned gold and then teleport away when they hit you. However, I have found a way to get the upper hand on the little green buggers. It requires certain conditions falling into place. Here is what you need:
1) enough weapons (darts, daggers, etc) to throw at and kill the leprechaun
2) another monster in the room with the leprechaun
3) enough health
Okay, when you enter a room with a monster and a leprechaun, aggrivate the leprechaun (if he is asleep) and the monster but make sure the monster can get to you before the leprechaun. Next run to a doorway and stand inside the doorway. Let the monster stand in front of you so it is attacking you. The leprechaun will come and stand next to the monster (at an angle to you) but will not be able to attack you since you are in the doorway. You cannot use melee attacks on the leprechaun but you can throw things at it from the doorway. See the diagram below:
In the situation above, you (@) are being attacked by a Kobol (K) and a Leprechaun (L). Make sure you DO NOT kill the kobol first.
Stay in the doorway and thow darts or daggers or shoot arrows at the Leprechan until it dies. Then you can kill the Kobol. Afterwards, go into the room and
help yourself to the items the leprechaun dropped.
This should work with any monster that can take things from you.