Blaster Master's Fgun
When you play Blaster Master, you start to notice that a lot of the powerups have letters on them that roughly correspond to what they do: pickups that increase your Power have a P on them, pickups that increase your Hover meter have an H on them, homing missiles also have an H on them, et cetera. But one of the ones that always perplexed me was the powerup for your gun in the overhead scenes. It had a little F on it for some reason.