The very prominent bass solo(?) towards the end of 'Special Brew' by Bad Manners. It's simple enough but after a catastrophic balls up once, it plays on my mind through the whole song, and you know what happens when you think too much about what you're playing.
We do a long, offbeat intro and slow verse of 'Chasing Cars' by Snow Patrol, which makes people wonder what the hell we're up to, then launch into a full fat ska version, which segues into 'Lip Up Fatty', then 'Special Brew'. All in probably over ten minutes long. As soon as we start my brain goes, "Ooh you f'd up the solo once and everyone stared, you'd better not do that again". And ten minutes of 'thinking' about it whilst playing is a surefire way to guarantee you'll f it up again, to the point that the rest of the band all turn to me in anticipation grinning. B'stards!