Sorry but people putting their bags on the seat is one of my hates! I know it stops unsavoury types from sitting next to you, but seats are for people not bags. I just hate hate hate walking down the bus/train and seeing a seat free but with a bag on it, and the owner sees me but pretends they haven't, and I'm forced to say 'Excuse me please'. The fact that they make you have to ask for it to be moved, when they know they're taking up a seat you want to sit on.
And then the look of disgust and hardship as they're forced to move their bag, sigh sigh oh woe is me. Then usually make a point of jabbing their leg or some other part into you for the entire journey to prove some kind of childish point.
Then there's the people who sit in the aisle seat, who when you make a move to try and appear to stand up just sit there. Knowing you want to get out and look at you out of the corner of their eye, so you have to go 'Excuse me please' and then the sighing and omg I actually have to move to let somebody out expression. Then taking 10 years to stand up so you're like sometime today please! As your stop/station rapidly approaches at mach 10.