Shared bike / walking path cocks..
Riders who refuse to move over for anyone, and paste that "I'm really hurting" expression on their face as if they're climbing the worst climb in the Giro D'Italia. Especially the ones on MTB's who definitely can't leave the bitumen and get dirt on their tyres.
And walkers who give stinkeye to any riders on the path, and who act all startled when a rider comes by, even though said rider has made all kinds of noises to alert them, slowed, moved over, doffed his cap to them, and so on.
Both sorts shit me and as a dog-walker and someone who very occasionally uses a bit of path to get home from a nearby trail I encounter them both.