Source: dc.wikia.com

7. Qwsp

No, not the cereal mascot. Different dude. Plus, that one's spelled Quisp.

This Qwsp is Aquaman's Mr. Mxyzptlk, in that he’s also a fifth-dimensional imp. However, Qwsp started off as a benevolent friend to Aquaman and Aqualad. He was just their good ol’ buddy. They even teamed up to fight a villain who'd kidnapped Qwsp's twin brother imp, Quink. They also teamed up to fight the evil water sprite Quirk. Hey, what's up with these naming schemes? None of the other fifth-dimensional imps have the stupid Q thing going on. Mr. Mxyzptlk doesn't. Bat-Mite doesn't. What's the deal?

But you're wondering why Qwsp is on this list. Well, when he was brought back decades later, he went to go find his buddy Aquaman, only to find that he was darker and angrier now. So Qwsp followed that trend, and eventually became a straight-up supervillain. He almost destroyed the earth, and he would have if the Justice League hadn't petitioned the other imps to stop him. He came back later, and almost destroyed all of the genies. But the JSA stopped him in maybe my favorite (or second-favorite) JSA story ever, Stealing Thunder.

Why he isn't more popular: Look, if Bat-Mite doesn't show up anymore, this dude sure isn't gonna make a comeback.