If you really put your mind to it, you can come up with something creative / clever pretty much no matter what they have written.

The BEST openers are inside joke / reference openers. You won't always find these / know these as it depends on your general knowledge / life experience.

Ex: If some one played WoW, you might work in a 'P.S. you no take candle' or some other joke that only a wow player would get.

It's far more effective than saying 'zomg I play wow as well, dats so kewl.' The first one builds rapport through emotion, the second builds it through logic (which doesn't work near as well)

Ex2: If someone works in retail, you might send something like, 'So How many times have you heard: "I don't see a tag, MUST BE FREEE HUEHUEHUE"?

What if they are really boring? Make stupid dadesque jokes.

Ex3: "I don't like playing games!!"

'I know you don't like playing games, but what about scrabble? I feel it's more of an educational activity!'

Ex4: No profile content at all, and photo is literally just a headshot with nothing out of the ordinary or comment worthy at all. Just say some random shit that's entertaining to you.

'What's your opinion on navy blue?'

'So, when are you planning on asking me out?'

'Is it too late now to say sorry?'

You can see literally anything as long as it's light and different that what they typically receive.