Since this was inspired by discussion in the MU thread, I'll start with
SLEEPWALKER:
A young man is haunted by a weird-ass green alien who is invading his dreams. It appears at random times, and vanishes after doing something with a crystal it keeps around its neck. During one lucid dream, Rick grabs the crystal away from the creature, hoping this will eliminate the nightmares.
Bad idea. It turns out this alien was a member of a sort of mental-plane police force called the Sleepwalkers. He'd been tricked by a villain called Cobweb into venturing into Rick's mind, and--now that Rick has inadvertently separated him from the crystal that allows him to travel through thoughts--is now trapped.
On the plus side, when Rick sleeps, Sleepwalker finds himself in the real world. Being a do-gooder cop by nature, he starts fighting supervillains. And he finds some really, really crazy ones. Think 1950s Batman Rogues Gallery, only sillier.
Surprisingly, the goofy villains and episodic nature of the storytelling work amazingly well. Bob Budiansky reaches a level of writing that he didn't even hint at on Transformers. And the artwork, initially by Brett Blevins, is abstract enough for a comic about a creature from the world of dreams, yet cartoony enough to match the simplicity of the storytelling.
Later issues got away from the original premise of the series, when Sleepwalker discovered that, unbeknownst to him, the other Sleepwalkers were planning an invasion of Earth and the story went more to multi-issue arcs focused on this, and the series was cancelled shortly afterwards.
For those who are asking, "Dude, what's the big deal? This guy never did anything," well, he played a pretty significant role in the Infinity Gauntlet series. Significant as in "everybody on Earth would be dead if not for him."
Here's a cover of Sleepy in his inevitable showdown with Nightmare, by a future Marvel EIC who should've stuck to drawing the pretty pictures:
