People who back into parking spaces rather than pull in them. Overall it's quicker and easier to back into an aisle over a small parking space, thus will save time and effort if done "normal." Bonus points for the people who back into spaces when they could have driven a few extra spots and just drive into a spot through to the next one, allowing them to drive out into an aisle and completely avoid backing up when parking and leaving. Sorry for the rant, however waiting for someone to back into a parking space is a huge pet peeve of mine.
Everyone in Hawaii does this and it drove me nuts. Especially because sometimes I'd have to sit there for five minutes as this person repeatedly tried to back into a spot (parking spots are tiny in Hawaii, probably due to lack of space). It's like, you're going to go backwards either going in or going out. Who cares this much?!