Oblivion: stealing plates. You will be chased down by the whole damned Imperial Guard for stealing an item worth zip, zero, nada, zilch and has no practical purpose. But somehow plates, cutlery, garden utensils, and all sorts of mundane items that have to cost more than a wedge of cheese don't and can land you with a bounty. What makes me mad about worthless plates? In Morrowind they all had a value and some, particularly early on, could add up to buy you that next set of armor. Best of all was one type of plate set that was worth TONS for being just something put on display (fancy china!).
Singularity: The Centurion Pistol. It's a great concept and could have been awesome if used in a similar role as the Bioshock revolver, but it's just sitting right now in my weapons locker. It's your first weapon but I would often just knife enemies because of a low total ammo stock and it being hard to come by when it was needed most. And then shortly after you find a freaking automatic assault rifle, a shotgun, and a bloody sniper rifle that can slow down time for headshots!