More of the small details that made a BIG impression!
1. Cutaway Diagrams: As a kid, one of my favorite little surprises in a comic book story would be when they'd feature a cutaway diagram of a superhero's (or superteam's) headquarters. The level of detail would always make the fictional world of the characters seem just a bit more real as living quarters and other human touches could be seen amongst the more familiar meeting, training or equipment rooms.
One of the most detailed (and consistent) diagrams was the Fantastic Four's Baxter Building headquarters (seen here), with other cutaway diagrams occasionally appearing in the Avengers, Superman, Justice League, and Batman titles.
2. The Spider-Signal: Yeah, Batman's much more high-profile Bat Signal is cool, but I like Spider-Man's spin on the concept, too. As a sort of "super-halogen" style light projector housed in his utility belt, Spidey is able to shine a giant circular version of his face mask design on walls or streets, thereby "announcing" his arrival at a crime scene. Seldom used against the "big fish", the Spider-Signal is primarily used to freak out small time criminals (and Connecticut Attorney General Richard Blumenthal).
3. Mogo: Long known for their dazzling diversity of life forms, the intergalactic police force known as the Green Lantern Corps had one member that topped them all in its almost incomprehensible immensity. First appearing in Green Lantern #188 (1985), Mogo was a sentient planet who operated as a Green Lantern (with a green equatorial stripe and lantern logo that made it look a bit like an giant striped billiard ball).
Springing from the fertile imagination of writer Alan Moore (who else?), Mogo's participation in the Corps has been somewhat limited considering it's planet-sized gravitational field puts a bit of a crimp in socializing or interacting with other standard-size life forms. It's current role is to serve as a training ground for newly-recruited Green Lanterns...and to remain one of the randomly coolest things in all of comicdom.