Bits of transphobia that I see regularly in the UK:
Whenever anyone in public sees me presenting female - make-up, clothes, body language etc. - and labels me as male because they recognise that I have a male body and voice. No excuses, you're not respecting me, it's transphobia. Especially people who do it deliberately, repeated "sir"-ing and "young man"-ing, and not apologising when I point out their mistake. It's humiliating, dehumanising, lazy and sometimes malicious.
When people make trans people out to be a joke - "I heard Lady Gaga wasn't always LADY, if you know whaddamean..." - it's like octogenarians saying someone "tends his allotment on Thursdays" or "butters her bread with a spoon" or something ridiculous like that instead of just saying "they're gay". By euphemising, they pathologise the thing, and it's never particularly funny.
When people just don't listen when told what certain things mean - "remind me, what does 'trans woman' mean again?" - No, you know what, I've explained it to you ten times, and it's not so bloody complicated. To be fair, this one isn't exactly transphobia, but it's people who clearly don't have basic respect for others as a priority.
These things all wind me up because they're socially acceptable, people get away with them all the time, saying "I'm open-minded, I'm not prejudiced" - well actually, this isn't about you and what you think you are. The things you say make me feel like crap, so bloody change it.
Sorry for the rant!