One thing that irritates me to no end is when first class passengers put their measly carry-on into the first bin, despite sitting in row 2 through 4.

There is nothing more annoying than boarding near the end of first class, having a seat in a row 1 bulkhead and then having to navigate all the way to row 4 to find overhead space because some knucklehead who is not in a bulkhead row can't put his knapsack under his feet or in the overhead that is above his own row. Then I end up fighting the sky priority traffic to get back to row 1 from row 4 and additionally have to fight the traffic back upon landing.