Retractable dog leads that seem designed just for tipping you off.
Volvo drivers. I saw one indicate this morning - nearly fell off in shock.
The guys who whizz past you and then pootle along at an even slower speed than you, so you're left with the dilemma of re-overtake and look like a twat, or hang back and wait til they bugger off.
Cyclist dismount signs.
Highways engineers who design cycle farcilities and have clearly not been near a bike since they were about 5.
But most of all me. As after 20 years of cycling, I remain utterly hopeless at all but the most simple of repairs and rubbish at remembering the names of various parts.