When I was 15, and this was a world (and a thousand walks) ago, I was 260lbs. and some guy actually asked me, in real life, if I worked out. All serious like, it was very awkward.
And someone also asked me, first thing they said to me, if I like swimming naked in public pools. But in this whole paedophilia way, not in a kooky way. I had a bad day with weird gay people at the time, so I almost ran screaming out of the room, ripping my clothes off.

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"Hey Ram, doesn't this cafeteria have a no-fags-allowed rule?"

SK and I were in the Starbucks on Astor Place complaining about some douche who cut in front of us on line in the Starbucks across the street. The guy standing in front of us, wearing bright red pants, turned around and said, "I can be a douche bag if you want me to," and smiled like an idiot.
The pickup line didn't work, but we'll remember it forever.

That could have been me, Manhattan. I am a gay pedophile living in T.O, afterall.

No, it couldn't have been me, cos I would never use a pick-up line in a million years.

"Oh my, you got a such a sexy accent, Where you from?"
"Russia"
"Oh really? what part?"
"Moscow"
"Do you like it here?"
"..." "I don't know, Do you like it here?"

Yeah, definitely the 'I can be a douche bag if you want me to' line was the worst.
There have been some other generic ones, but that one was definitely the worst.