The Legionnaires: Bouncing Boy
Bouncing Boy, aka Chuck Taine of Earth, aka Charles Foster Taine. Created by Jerry Siegel and Jim Mooney.
Quick synopsis: Chuck Taine, while slacking off from work one day, accidentally drank an experimental formula that allowed him to turn himself into a giant bouncing ball whenever he wanted. He parlayed this dubious blessing into a Legion membership that was interrupted by the loss of his powers several times, and eventually married and retired to run the Legion Academy. In the reboot he didn't have any powers but became a full-fledged Legionnaire anyway as the team's resident engineer.
Mark Waid gets Bouncing Boy. He once said something like, "I think a big fat 250 lb. guy hurtling at you at a hundred miles an hour is a damn cool superpower." Of course it is! You don't want to fight Bouncing Boy; he'll clean you right up. Not much compared to Mon-El and the White Witch, maybe, but it's a perfectly effective street-level superpower.
It has been said many times that the great thing about Bouncing Boy is that he got to marry Triplicate Girl (well, Duo Damsel, anyway). I don't have anything interesting to say about that, but I know that if I didn't mention it, somebody else would.
What I like about him is that he's got one of the few superpowers that would actually be fun to use. Most superpowers, you could do fun things with them, maybe, but they aren't fun themselves. (Flight would be another one.) Seriously. Wouldn't you like to ricochet all over the place if you knew you couldn't get hurt? Sure you would.
Bouncing Boy became an instructor at the Legion Academy after retiring from the Legion early in the Levitz run. Consider these two scenes. In the first one, from LSHv2 #304, Bouncing Boy is leading three Academy students plus new Legionnaires Invisible Kid and the White Witch to capture some escaped zoo animals.
In the second one (my pick as Chuck's signature moment), from deep in 5YL territory (LSHv4 #17), Bouncing Boy and some others are trying to survive the Khundish invasion of Xolnar.
This is what's so great about comic book continuity. The second scene works just fine by itself, but you get a lot more from it if you've read the first scene too. I don't even know for sure if Giffen and the Bierbaums had the first scene in mind when they came up with the second scene (but I figure they probably did), but I do when I read it, and it resonates.