Idiot Ball/Fan Works

In Neon Genesis Evangelion: Nobody Dies, Kaworu is very enthusiastic about maintaining the species with Rei. The Idiot Ball? The first attempt fails by loss of Ocular Virginity. The second by Defenestration. He still tries.
Played for Laughs in the Kingdom Hearts: Birth By Sleep fanfic Reaching the Understanding, which turns Terra's tendency to be overly trusting of the wrong sort of people into a Running Gag by way of a chain of Gilligan Cuts.
In the Firefly/Doctor Who crossover fanfic The Man With No Name, some of the characters are hunting Reavers. When they stop, thinking they've heard something, the Doctor keeps going anyway, walking smack right into one. Even the Doctor admits it was blindingly stupid.
- Being fair, the Doctor is the only person there who has absolutely zero knowledge of what Reavers are.
The goal of Harry Potter and the Methods of Rationality seems to be to avert this.
- Although, it does get a lampshade in chapter 63, when Moody mentions a drug called "Bahl's Stupefaction", the effects of which include causing the user to do extremely stupid things.
The cast of Hogwarts Exposed grab the Idiot Ball frequently, but special mention has to go to the scene in which Harry, Hermione and the entire Hogwarts faculty get outwitted by Crabbe and Goyle.