My personal least favorite type i encounter on the trails, is the person (usually a women) walking a dog (usually quite small and fluffy) that's on a retractable leash and the bloody leash is all the way out (like 30ft out). Fido is on one side of the trail, and dog owner usually on cellphone and or texting is on the opposite side of the trail completely oblivious they are about to cause some serious harm to either the dog, or the cyclist......or both. And usually said dog owner moves slower than a sloth (hence the need for a 30 ft leash) so you end up either braking and going really slow or come to a full stop.
On the upside at least the dog is actually on a leash.