INFPs are incredibly easy to tease. If you want a demonstration of this, simply tell them that the negative outcome of a scenario was their fault even though they clearly had good intentions. They'll immediately show a sad puppy face. This emotional trolling works for a whole range of situations too.
I have this nasty ESTJ shadow though. It's less sad puppy dog face than cat backed into a corner and hissing menacingly face.
My sensitivity tends towards the angry, defensive side of reacting, not tears.
Admittedly, this puts people on egg shells sometimes, as they actually get afraid of you and will give you your way. It's not a positive thing, but it gives you a sense of power, and I suppose when you're stressed and upset, that's what you're trying to retain.
"Charlotte sometimes dreams a wall around herself. But it's always with love - So much love it looks like everything else. Charlotte Sometimes - So far away, glass sealed and pretty." - The Cure
When I first met my INFP friend, I used to joke around and poke fun at her all the time. See, I have the problem of assuming that everyone likes to play joke/make-fun of each other for fun like I do. This wasn't the case with the INFP. At first she would play along a little and give a sad sort of laugh of reluctance, but then after a while she'd do the stare tactic or the complete ignore, so I cut back. More recently, however, she'd give a perfectly calm and serious defense of the behavior I was mocking, which is just no fun at all.
In any case, though, it would only be fun if I completely outraged her, because otherwise she isn't the type that strikes back to keep the banter going.