Yeah… on the DC side, there's pretty much most of the guys of Young Justice. And Nightwing's never portrayed as beefy, either.
You could also go Marvel Cosmic- Star Lord from the comics is Average-Joe-ish, as well as most of the lesser known male cast like Jack Flag and Adam Warlock. They do have some musle, but they're no Drax or Hulk.
Iron Man/Tony Stark's another option, too. And Robert Downey Jr is really short to boot.
NY COmic Con: '06, '08, '09, '14
Otakon: '07, '08, '09, '10, '11, '12, '13, '14
Katsucon: '10, '15
Animenext: '10, '11, '14