Boomdagger is a bonus giving treasure card in Unnatural Axe.
Flavor Text Edit
"+1 Bonus. Usable by Thief Only. If stolen, lost to a curse, or sold to buy a level, this throwing dagger returns to the owner at the beginning of his next turn. If traded, looted, or given away, it becomes faithful to the new owner. It is only lost permanently to death or Bad Stuff.
The Boomdagger gives +1 Bonus, but it is only usable by Thief. However, it has two interesting gimmicks. The first one is that it takes 0 Hands to play. The second one is that, on being sold, stolen, or lost, it returns to the owner on his next turn. This works basically as an infinite 100 Gold, or infinite 1 Bonus.