The lane-wanderers are annoying, oh yes.  So are the ones who ride their brake pedal, so you never really know whether they're slowing/stopping or just resting their left foot.  

But tops are those who, puttering along when entering a construction zone where one lane is closed, seem to think that there is no need to merge over to the open lane till the last possible second before the barracades and everyone is just supposed to stop and let them in line.   And the jack*** who drives like a maniac alongside traffic that has already merged over to the open lane and then signals/honks/gestures/cusses to get in line.......like he's so important that he must be allowed in front.  Ain't happenin' if I can help it.