An ex of mine used to do impressions from Blackadder, in particular saying the word "etty-quetty" at every opportunity. I wanted to stab him in the eye.
That on it's own probably wouldn't have been enough to break up with him for but he was also tight-fisted (he gave me a jar of humbugs, a set of books worth £1.25 each and a boomerang for our first Christmas together and they were all secondhand as they'd been sat on the shelves of his bedroom since we first met) and he wasn't skint either, just tight. He'd spent several months hinting at wanting a new watch and a Discman player (90's) from me so I should have run a mile then.
He was selfish, attempted to be unfaithful at least three times (and failed as far as I know but only thanks to those three women having better taste than I obviously did) and for some reason he decided that he wanted to model his appearance on Vladimir Lenin, something he still thinks suits him to this day.
Worst of all, and this is the very worst, during a stop off in Thailand on the way to Australia he bought a pair of black silk pyjamas which he insisted on wearing all the time when he was at home because he thought they made him look like James Bond, and a purple silk shirt with big white flowers on it and his mother, father and brother all bought identical shirts which they wore without irony or shame when out together! Everywhere. And I had a similar one from C&A that I had to put in the bin because of the horror of it all! 
His mother still wears hers!
When he proposed to me in front of a jewellers window in a packed shopping centre at Christmas the only possible thing to do was say "Oh my God, NO!" and run for my life.
A lovely ex who just wasn't the one used to exclaim "oh my word…oh my giddy aunt" during sex, so that was obviously never going to work out.
And the one who mis-interperated my valentine card as a death-threat and turned out to be using me to make another woman jealous. Which didn't work so he left me for the other woman's sister and ended up being beaten up by her not-quite-ex boyfriend when he got out of prison. Lucky escape with that one. He was short, stupid and very bad in bed but for six insane weeks I did my best to convince myself otherwise.
The valentine card was quite a simple one, it said "Guess who…" on the front and "…loves you?" on the inside. He decided that the 'Guess who' part was a threatening message from someone who had previously threatened to beat him up and he went into hiding for three days which meant he made his mum answer the door and his phone while he stayed in his bedroom
Fortunately at this point I met DH, who is lovely, mostly normal, and doesn't dress like his mother, reference female relatives during sex or assume that Hallmark are agents of the mafia.