I can honestly say pretty much nothing. I met my girlfriend on the 26th of April last year, and to my recollection which is pretty accurate about these things, I haven't cried once during the (almost) year that's preceded, and before then I can't recall so easily. I've never cried when at funerals or anything, be they of close or distant family members, and i've never cried during any movies either, nor did I cry before or after the surgery a couple of years ago which involved the bones in my feet getting broken/shaved/reset.
I think i'm the stereotypical stiff-upper-lip guy, only that statement often implies that emotion is being held back which it really isn't for me as they're not there in the first place. I sometimes worry, stressed, bored, and I often get angry (pretty much any time I have to drive anywhere as there's always someone on the road whom fate decrees will be the individual to get horribly in my way), but so too am I very often in a positive mood, unafraid to laugh and joke, and have a good conversation about interesting things, but crying really isn't a 'thing' for me; perhaps something will come along in life to change that naturally, but from my past experiences thus far it would have to be a pretty big thing; the birth of my first child perhaps, but then that would be tears of joy in any case.