Fast. Sexy. Hard to catch.
Batman has his Catwoman, and particle physicists have to contend with the elusive -- and possible erroneous -- existence of tachyons. One's a sexy burglar dressed in leather, and the other is a subatomic particle that travels faster than the speed of light.
I know what you're wondering: How can a tachyon travel faster than the speed of light if light speed is indeed the "universal speed limit"? That's like saying "no ducks can wear pants," and then the camera pans over to a mallard wearing friggin' corduroys. We have universal laws for a reason, people.
It gets even worse: If the principles of special relativity hold true, tachyons aren't just breaking the universal speed limit, they're also violating causality itself. In this universe at least, cause always comes before effect. Without that law in effect, the fabric of the universe unravels.
If tachyons exist, it's likely due to this loophole: While relativity prevents matter from accelerating to the speed of light (as this would require infinite energy), it doesn't apply to particles that always travel faster than light. For tachyons, the minimum speed is the speed of light, and it would necessitate infinite energy just to slow them down to subluminal speeds.
Tachyons: They're total speed demons, and they might just actually exist.