Ugh I know right? Not to be offensive but out-of-touch nerds are the worst. They have no concept of boundries and their idea of flirtation isn't "I think you're beautiful and interesting and want to get to know you better" it's well come to think of it it's nothing I should repeat here!
It's not. And then they wonder why people don't want their flirtation.
Then of course comes the name calling when you dare to reject them bluntly and the other names when you try to be subtle.
The worst part is how many of them act like I have to be nice to them even when they're intruding on my time and in my space. *rubs temples* Must not go into OT rant mode...
I'm not going to lie, I'm usually flattered by the interest, and consequently I let people know politely that unfortunately I don't return it. There are very few situations where I've ever been grossed out by someone attempting to flirt with me, and both involved rather unhygienic men over the age of 50. One of them didn't really flirt as such, he just sat down blocking my exit and told me he was going to buy me a drink and I was going to sleep with him in payment. He had no teeth to speak of and made my skin crawl- and I still said "no thank you, I'm engaged" politely and sat there like a frozen rabbit until my fiance rescued me 
D: *hugs* I know that frozen rabbit feel 
Though honestly the sheer bluntness of that is just hilariously awkward. Did he seriously think you'd say yes?
I just don't understand that mindset.
But honestly I rather just have all the flirts initiated by the player but that's just my preference. The whole compliment that you can take at face value or flirt back also works for me.
For me the worst people are the "Personal space? What personal space?" people who seem to think the closer they get the luckier they will be
awful lines I can usually handle with a smile but I'm not a "lets practically sit in her lap" or "lets do the touchy-arm, touchy-hair thing" kind of girl.
OMG. This reminded me of this weird dude I didn't even know sat next to me, put his arm around my shoulders (my face at this point is a mixture of WTF and is this real life?) and proceeds to tell me I'm pretty and do I want to kiss him while blatantly staring at my chest. I froze for a good 10 seconds in sheer shock at the audacity before removing his arm from my shoulders and of course that jerk kept touching me and when I tried to leave the room blocked my way until I pretty much threatened to call the cops (campus police but still). God that memory is so wtf. (Please note I said I wasn't interested at least a dozen times he kept brushing it off).