I hate it when people try to let you out when your trying to make a left turn somewhere. I understand they are trying to be nice, but.. it just causes confusion. Like today I was trying to make a left and this guy stops his car to let me go (and there are also cars behind him) and hes motioning me to go.. without looking for me and there is pretty much constant non stop traffic coming from the other lane. So then he gets pissed off when I'm sitting there for 30 seconds not turning (because he was obviously too dumb to noticing on coming cars preventing me from turning)
TL;DR Don't stop traffic to let somebody in; it causes confusion and wrecks. People behind you don't expect you to be stopping on a main road if your not turning. Also if somebody is trying to let you in, because they are dumb enough to stop cars behind them (thus defeating the purpose of the good deed..)they are probably dumb enough to not look for on coming traffic for you.
Picture representation:
One of my driving pet peeves along with people who don't know how to use a turn about or a 4 way stop.