Uh, two really bad ones stand out:

• A group interview (2 people) where the company wanted us to collaborate on a node.js project that sent templated emails. I had no experience with it (I mentioned front-end experience with AngularJS) and the other person did. The interviewers expectation was that by working together, the other person would teach me enough to do my part. Obviously, the other person just did his component and didn't bother, so I was still working out the basics and he ended up with the job (I know because I heard the interviewer talking shit about me to him and saying she'd "really" be in touch).
• For a C/C++ position, I was told I would have to take a multiple choice quiz. I was like 8 years experienced in the languages and really pushed that it'd be no biggie. I ended up bombing this clusterfuck (or one of the others from the same site). The questions are nauseating, some underhanded, some really obscure, and I can imagine the process only favors whoever guesses best (I got 70%). This is in America, btw.