Slow-walker

A selfish, unaware ass with no respect for anyone else's time. The bane of impatient people, and everyone else's existence, they will walk slower than previously thought possible, making sure to be in the center of the walkway and moving side to side while walking so no one could possibly pass them. They also like to stop in the middle of walkways to talk with friends and to act surprised when you get annoyed and ask them to move. The most efficient way to deal with such people is to (as rudely as possible) tell them to move.

OMG, you're such a slow-walker, move, my grandmother walks faster than you.