The fun part about crafting custom loot is coming up with different ways to break the balance of the game-- slightly. Sometimes, though, I don't think things through as much as I should.
Take the Merciless Longbow of Bleeding, which does double-damage when the target is bloodied. 2d10+2+the DEX modifier bonus is a lot of damage, sure, but it's not a ridiculous amount of damage.
But when the ranger uses Twin Strike with her Merciless Longbow of Bleeding, she's doing 4d10+2+DEX modifier damage. Oh, plus 1d8 Hunter's Quarry. That's potentially over 50 points of damage. For a level-three character using an at-will power, that's the very definition of ridiculous.
Moral of the story: be smarter than Tom. Not a particularly difficult task, to be sure...