This is a pretty broad question… guess it depends on what you think is kinky or kinks your into. So ill list a few things.
Cumplay (of various sorts)
Swinging / partner swapping
3somes
Group
Gangbang
Anal play
Foot fetish play
Outdoor (in nature) / public play (dressing room, restroom, park at night etc)
Role-playing
Risky sex (breeding / impregnate)
I could list a few more but this what was on top of my head
So in a sudden act of spontaneity, my OH stuffed HER knickers up MY bum during sex last night. Odd but strangely errr……ok
@marbles1 . You mean like a wedgie " up"or actually " up" 
Just curious, certainly different.
Like actually up, as in not a wedgie.
Apparently it’s a thing but I didn’t know so it came as quite a shock!
Very unusual and a little disconcerting but hey….it wasn’t a bad experience and the whole surprise aspect made it more sexy than it probably sounds.
Fair enough, i’d certainly imagine it would come as a surprise.
I was totally unaware of it being " a thing" , but hey, there you go, who knew.?
Bye the way, was it a skimpy thong or the full Bridget Jones variety ?
I’ve definitely put underwear (mine and theirs) up previous partners, and also had sex with them whilst it’s in… never occurred to me to put it up their bum though!
Kinda in between I guess. Just nice silky Brazilian knicks in black. Quite a luxury set in fact so I was a little surprised OH was willing to put them through the trauma!
Started off by simply inserting her index finger but through the material of the underwear so it pushed it in too, and just sort of went from there.
Very odd…felt like a prostate massage but not as intense, along with a sort of filled feeling like being pegged but again not as intense (or as deep).
Then tugged them out bit by bit while sucking me off.
Tingley, tickley and highly recommended! 
That could’ve been very traumatic lol fair play
I can see the attraction.
I’ve got some strappy wet look shorts that I sometimes wear when my wife and I are fugging. She pulls on them as I cum. It feels really good!
Licking up and eating my own cum. We hadn’t had sex for six days. Last night wife began blowing me and fingering my ass. She tied my hands to the head board. She put nipple clamps on me and then inserted my Mantric prostate massager. She would softly lick and massage around my cock while having prostate orgasms. So much precum and cum was flowing out and she would put it on my fingers to lick off. When I finally orgasmed and it was a big load she would feed it off her fingers to me or lick it up and kiss me. So hot and so glad no judgment on her end.
Pegging, anal, threesomes, spitting, cum play … roleplay, edging … all kinky 
This may not be kinky, but we are naked outside in our backyard a lot. It’s private, so day or night, we can be out there. We’ve had sex outside lots since moving here.
My wife did that once, while fooling around she stuffed a pair of her silky knickers up herself so they got all wet and I licked her to help with this. Then before we had PIV she pulled them out all soaked, put them in my mouth, taped it up and made me keep them in while we had sex.
That was so hot.