Lol, these are brilliant!
There was the one who messaged me on OLD and I answered because nothing ventured nothing gained. After chatting for a couple of minutes and him making a couple of creepy suggestive remarks I told him that I didn't think I was interested but wished him well... What followed was the most bizarre drawn out "it's not you its me" conversation with him getting more and more aggressive because, what did I mean he wasn't my type, he was a nice man, was I not looking for a nice man? So what was my problem, why wouldn't I date him?
Or the one I exchanged a few emails with (OLD again) and agreed to talk to on the phone. There was no chemistry and he was dull as anything so I emailed him to say that he seemed nice but no chemistry so I didn't want to meet. He then spent a week messaging me about how he would never find anyone else like me and he had to be with me because I was the only one for him and no one else would get him like me. 
Then there was the one (oh look OLD) who I went on a date with to my favourite pub, he started by insulting said pub, followed by mocking me for having a soft drink (I was driving) and then stood in silence for the duration of that drink leaving me to fill the void, I did try shutting up in the hope that doing so would illicit some form of communication from him but all he did was say "what? What's wrong?" At the end of the drink he said "right, you only promised to have one drink with me so what do you want to do now?" I made a lame excuse about going home because I had to work. He then followed me to my car and stood behind it and wouldn't move... It was very awkward and I ended up shaking his hand and saying "nice to meet you" in an effort to dismiss him.
I thought that was the end but he then texted me when I got home to ask me how I thought it went. I told him there was no chemistry but wished him well, he then went on to tell me that it was my fault as he would have snogged me if I hadn't been so weird and shaken his hand. I informed him that had he done that I would have broken his jaw so it was probably for the best.
That didn't stop him texting me to ask me out a month later. Err no, or when I showed a friend his profile while telling her the story texting me again to say "I see you've been looking at my profile, you're still interested then?" Or texting me a month after that when I just pretended that I had no idea who he was until he got the picture.
Then there was "the devourer" nice enough bloke but dull as dish water. Decided to kiss me on our second date and by kiss I mean open his mouth as wide as possible and place it over my face as I recoiled. I informed him by text that this was not good as I just couldn't bare for it to happen again and he informed me that he'd had several relationships and none of them had suggested he wasn't a good kisser. I reluctantly agreed that we could work on the kissing and went on another date but at the end of it he tried to eat my face again and that was the end of that.
Oh and then there was the guy I dated for about a year. I suggested that we take a break so he pulled a knife on me and was surprise when I said it was over
For years after he used to contact mutual friends and tell them how he still loved me and didn't understand why I didn't want him but would then in the same breath tell them I was an evil gold digging cow (he was always broke and scrounging off of me), whenever he saw me he would ask me for a hug and get aggressive when I said no and asked him to leave me alone.
It eventually stopped about 3 years later when he met someone who was a friend of mine and cornered her trying to get her to tell him what I'd been up to and if I was seeing anyone etc. giving her the, but I love Runner routine, unfortunately he made the mistake of asking her if I ever spoke about him. Her response (love her) was "not really, she just mentioned that you were a bit of a psychopathic shit..." Apparently he went mad about how much of a cow I was and then never mentioned me or bothered me again 
I'm sure there's more OLD is a minefield but luckily I met my wonderful DP IRL and shall be holding onto him for dear life! 