3. Ultimate Nullifier (Marvel)
To immediately instil the power of the Ultimate Nullifier in to your mind, get this - it's the only known weapon in the Marvel universe to inspire fear in the planet-devouring cosmic entity, Galactus. On the surface, it appears to be a small, hand-held metallic device with no obvious functionality. However, it has been described as "the universe's most devastating weapon." It has the ability to completely eliminate any target the wielder chooses (along with the wielder themselves if his or her mind is not focused enough on the task at hand). In the hands of a being with an extremely powerful mind, the Ultimate Nullifier can destroy (or in conjunction recreate) entire time-lines from beginning to end - essentially meaning that it can erase or create entire planes of existence in a single action. If Galactus appears on screen any time soon, the Fantastic Four could do worse than getting their hands on this little doozy (which is easier said than done, given that it's often in Galactus' possession in the first place) in order to scare him off before he eats Earth.