Far and away my biggest pet peeve while running is in passing runners going the opposite direction and waving, saying hi, etc., and getting nothing in reply.  I understand how this could happen in a big city, but in small towns it's inexcusable.  At least give me a grunt...

I can understand LowDead's peeve about the competitive runners that finish a race and then turn back. I can't speak for other's, but I often run back after finishing to support a friend who is still out running. If I just wanted to run some more, I wouldn't run back, but instead, just keep going, or do the course again.

1. People or people with animals, prams, ect who block the path and won't budge

2. People smoking where runners are likely to be eg in parks, or on footpaths

3. People who leave their dog's excrement on the ground - they should have a dna databank for dogs and a free drop off service for dna testing of dog pooh. Owner pays for costs.

4. Idiots who yell from cars and throw objects at you or drive as close as they can to you even if it is 6am on a sunday and there is no other traffic on the roads.

5. Competitive runners in large groups who refuse to share a path with other oncoming runners

6. Cyclists who use both sidea of a shared pathway and ride as fast as they can along the windy paths

SO many of mine have been addressed, but here they are again:

1. People who don't move to the side of the path, either coming towards me (uh, hello - I WILL run you down, dummy) or who, when I yell out "On your left" or "Coming through" insist on staying where they are or turning around to see just WHAT is it that's on their left or coming through? like it's a mystery.

2. The folks who group up to walk together - four abreast, of course.

3. The bikers/rollerbladers who zip by with about an inch of clearance.

1) Most of what others have stated!

2) ) Pet peeve happens almost every run. I run around San Diego Mission Bay on an ocean/bay boardwalk. It can be busy with walkers, dog walkers, and bikes. However I run in the evenings or early am so it's about 95% fitness people on it. You get in the habit of looking behind you before passing. Anyways there's always one arsewhole who cannot stay on the correct side (it seems to always be a walker, although sometimes it will be another runner), who insists on walking/running on the left side, opposite every one else (basically head on with you not following on the keep right rule, which is clearly outlined on some signs scattered throughout the park). Mind you there's no cars, so the only reason is some weird psycho power trip or I don't know what else. This doubly geeks me up as I have poor vision in my right eye and my peripherial vision sucks so I like to stay to the right and not get into the middle of the path. Most of the time I just plow right into them and play chicken. It's a personal mission I'm on now. I need to mellow out I guess!

3) As someone else pointed out the running clubs/groups that insist on taking up the entire 10' wide sidewalk, 3 - 4 abreast running straight at you. 

RunTedRun - I always want to yell at the wrong-siders "Do you drive on the wrong side TOO?"

but usually I'm too out of breath to do anything but mentally swear at them.

And I can top being bested by a stroller - on one of my worse runs, I was passed by a weiner dog. In my defense that little guy was booking along.

Drivers who back out of their driveways without looking.

Mountain bikers on trails who don't announce they are behind me and I have to dive into poison oak. Also, mountain bikers who don't acknowledge that I have nicely stopped and stepped off the trail so they can pass. A simple thanks or smile or wave wouldn't kill you, dudes.

Ginormous strollers, too. Particularly those that have a four-year-old in them. Why can't kids walk any more?

i hate it when  people will ask you how far u ran, and when people stop you to ask where something is. and the most important when i run i run at night, and people will turn on there brights when they are about to pass me and it blinds me.

Things that bug me while running:

Dead animals on the side of the road  ,  The bird **** under the bridge , The beautful smells  coming  from the Panaderia as I run by ,  The guy  that work at the gas station that keeps changing  the price for a bottle water on my long runs , and of course the cars that cut me off.........Side note :..One time a car cut me off as I ran  across the crosswalk , he nearly  hit me so I threw my water bottle at his car , after it hit his trunk and bumper  he continued on , and then I realized that I still had 5 + miles to go on my long run and that I needed that bottle...Oh the shame of running over to pick up the water bottle.....  .