Mine, in no particular order:

• threesome
• sex with 2 women
• be watched by others while having sex
• watch others having sex
• sex in public like a beach or a park, i.e. out in the open (day or night is fine)
• sex in a semi-public place like a public restroom, etc
• sex in water (man made like a pool or hot tub)
• sex in water (natural like the ocean or a lake)
• moresome/orgy
• sex in a moving vehicle
• sex in a parked vehicle
• sex with a total stranger(s)
• sex with an older woman (current "record holder" is 25 years my senior)
• Sex with a much younger woman (current "record holder" is 3 years younger than me)
• Blowjob while driving
• sexytimes in my seat on a plane
• join the mile high club

EDIT Added some things to my list

That's all I can think of currently, I'm sure more stuff will pop up!