A friend of mine at GUGS who goes by the nickname of Doc runs superhero one-shots every now and then using a simple homebrew percentile system (characters are assumed to be awesome 70% of the time, so if you roll above 30 you're generally okay, though you might get extra special outcomes for rolling specific numbers based on the years of publication for notable comic books). They're always a lot of fun. Most recently he has been running one-shots revolving around the Glasgow Avengers (now appearing as the Pure Super Pals over on Doc's website).
The characters alone are a recipe for hilarity. I played the Magenta Munitionist whose superpower is to be able to pull any weapon from anywhere in the multiverse out of her pocket, and her niece was Quantabella whose superpower is to shoot probability-altering beams through her Cyclops-style visor. When Quantabella used this power for mischief or with terrible consequences (either of which happened more frequently than not) it was usually followed by her aunt's anguished cries of "Quan-ta-BELL-AAAAAAAAAAAAAAAAAA!"
There's also Super-Rab (basically what would have happened if Superman had landed in Easterhouse rather than Smallville), the Duck (Batman except with a duck mask instead of a bat suit), and the Fractured Friar (who exists simultaneously across all possible universes, which gets a bit confusing) to name a few.
Most of the humour comes just from this horrid bunch being unleashed on the would-be supervillains of Glasgow, but also from Doc's characterisation of the various NPCs (such as the Pure Super Pals' landlady, whose name escapes me at the moment). I sadly won't be able to participate in his upcoming one-shots at GUGS during the Freshers intro weeks since I'll be running my own, but I'd love to play in another Glasgow Avengers/Pure Super Pals game sometime in the future. Or just ANY game Doc runs in the future, because he runs AWESOME games. (See the New Runaways/X-Men: Last Class campaign from 2012-2013 for an example.)