Choices (I think I got em all):
Anecdotties - A one-off Xfm feature where Adam and Joe told their summer anecdotes to a caller in order to find out whose were more interesting
Celebrity Regression - A regular Xfm feature where Joe would regress Adam into a state of celebrity regression, from which Adam would see relive scenes from a famous actor's films. Callers had to guess which actor Adam was inhabiting.
Crap Commentary Corner- A long-running Xfm feature where Joe (and sometimes Adam) chose select clips from crap DVD commentaries, and callers had to guess who the commentators were. Alternate explanation: It's a crap commen-t'ry, recorded off of-a D-V-D, why don't you call in-and-see, you could win some crap-for-free.
Each Passing Minute - A one-off Xfm feature parodying Radio 4 afternoon plays. Planned to be a running series whose narrative would be 'steered' by the listeners, but lasting for only one glorious week.
Movie Lingo Bingo - A semi-frequent Xfm feature which involved Joe playing clips from famous films with a foreign language audio dub. Created after Joe ran out of DVDs with an amusing commentary audio.
OTTFX - a short-lived Xfm feature in which Joe chose movie clips which employed a ridiculously Over The Top sound eFX to illustrate a mundane action. Callers had to guess which action the sound accompanied. They usually didn't.
Rock 'n' Real or Rock 'n' Rubs - An Xfm feature where Adam would read out 10 band names - 5 from the NME and 5 from his brain. The caller had to guess which were real and which were rubs.
Song Wars- Adam and Joe compose short songs on a common theme, e.g. Public Transport or Birthdays, and invite listeners to vote for their favourite. The favourite gets played the next week as well.
Pop Psychology - A BBC6Music feature where Adam and Joe interview a caller and diagnose the mental problems of their aspiring band, prescribing solutions for their issues.
--
I didn't include 'Text the Nation' as a feature, as they've always asked listeners to call/ email/ text in about a subject, there's no competitive element and Adam and Joe don't do anything except come up with the theme.
If you haven't heard the Xfm podcasts or shows, you might not have much of a choice, seeing as the BBC6Music shows have only had a couple of features so far.
I voted for Crap Commentary Corner. I think it perfectly sums up their hilarious attention to both pop culture and minutia, also evident in their deconstruction of adverts. Joe uncovered some really incredible finds, such as the Tom Clancy one on the Sum of All Fears.