Possible Prizes

10% Discount Card - (usable at NPC vendors)
Fixed Pipe (unique item - apparently, it stops you spawning from battle - not confirmed though)
Amity Jelly (+10 Amity)
Steel Hammer (-99 Speed when equipped)
Forgotten Scroll (reset's 1 stat point)
Baked Potato (depletes an enemy's SP in battle)

I didn't see anything that lists all the prizes but those are some of the prizes that a guy listed in his thread. Here's a link to it :)
http://forum.wl.igg.com/viewthread.php?tid=3149...
hope this helps :)