Jon at Facedown in the Gutters has a funny bit up about Green Arrow, wherein his girlfriend speculates that GA's power or function within the Justice League is to "point at things." Honestly, if that were the case, he wouldn't be any more useless than he currently is. It might even be better, all things considered.
Green Arrow is, of course, Oliver Queen, who began his comics existence as a pale imitation of Batman: millionaire playboy who trained himself to be the best in the world at a particular skill (archery, in this case, natch), began fighting crime and acquired a
buttboy young ward/sidekick. In those early days, he even had an Arrowcave beneath his mansion in which he stored the Arrowmobile. Batman was understandably pissed, but after consulting with his lawyers, he determined that he could trademark neither narcissistic themed gadgetry nor pedo-homoerotic sidekickery.
Anyway, at some point in the '60s, the powers that be at DC decided that GA was pretty lame, so they revamped him. He lost his fortune, his sidekick broke up with him and got hooked on smack, and somebody decided that GA was going to be a bleeding heart liberal, crusading for the rights of the poor and downtrodden, which basically meant that he went around complaining about "fat-cats" a lot and shooting arrows at guys in business suits who smoked cigars. He's been at it for a good 40 years now, with a brief break in the late '90s when he was dead.
Anyway, the great thing about Green Arrow and his mad archery skillz is that's all he's got. I mean, there's nothing wrong with being the World's Greatest Archer. It's gotta be a pretty good gig, overall. Go out and win a few Olympic medals, then sit back and wait for the endorsement checks from archery-supply companies to roll in, right? "Hi, I'm Olympic Gold Medalist archer Ollie Queen, and I rely on Allen brand bow-string wax..." Naw, that ain't how superhero comics work. If you're the World's Greatest Anydamnthing and you live in the DC (or Marvel) Universe, you go get yourself a costume and start fighting crime.
And that's the amazing thing. Green Arrow is a perennial member of the Justice League. The Justice League, for God's sake! They've got a guy who can fly, shoot heat rays from his eyes and is strong enough to push the moon around, a woman who's on a first-name basis with the Greek Gods, a guy who can run at the speed of light, a guy who wields what is commonly referred to as the most powerful weapon in the universe...and Batman's clearly got the whole "guy who has no powers but is cool enough to hang out with the super-powered folks anyway" angle locked up. Green Arrow? He shoots arrows. Yeah, he does it really well...but is it really that useful a tool, speaking in a superheroic sense?
Look, Aquaman gets a bad rap, but at least he's the frickin' King of Atlantis. No, it's not a tremendously useful thing, but if any crime or natural disaster should happen to occur underwater, the King of Atlantis is going to be handy to have around, right? Green Arrow doesn't even have that going for him. And therein lies the key requirement to be one of the World's Most Useless Superheroes. If you're more useless than Aquaman, you make the cut.
That's right, I said it: Green Arrow is more useless than Aquaman.