Mine seems pretty tame compared to some that I read
But I guess I'd have to say:
Changing room of a swimming pool
Dressing room of a clothing store

Sounds good to me, Lex....

Well that's ok then Thankyou.

On an open field beneath a tree. It was awkward, at first, but fun.

At a water park. The Lazy River didn't feel so lazy for once.

On my way to New Mexico,at night, on my motorcycle.

In the ladies rest room at a bar. Pure luck no one walked in on us^^

Gandalf wrote:On my way to New Mexico,at night, on my motorcycle.

...and blindfold while juggling six axes too, I bet

Ah ye nonbelievers,actually my bike was better suited for it then this guys stock bike.
Mine was a low slung 65 Harley chopper with highway pegs,nothing to it.
http://www.youtube.com/watch?v=WnXIfXLqmIg

For me it was in a half meter deep lake near the beach. We were on a kung fu camp and my partner was an instructor girl at master level...near mistress level

and also on a nudist beach...but that is usual if you are careful and doesnt disturb others.

Okay, some quite wild ones out there.

My wildest (s)experiences

1. With my girl out in an unknown forest, but merely 20 meters from someones back garden (heavy petting and oral)
2. Same girl, other forest: less than 10 meters from the fence of a very large public swimming pool. The fence was hidden by a large hedge, but anyone on the other side could easily have seen us. We only found that out later.
3. Same girl, the same public pool, now inside the fence on the large open, crowded lawn area, on our towels, her beneath a large beach towel, me fondling and fingering her
4. on top of the 10 meter concrete dive board, fingering her, no cover, but sitting down (note, the pool area is built into a hill side overlooking the pool area, so the people on the rising hill easily can see the top of the dive board
5. second girl, another semi-public pool (now you would say Spa) with a sauna and tanning booths, in an unused tanning booth off to the side (note these tanning booths are in the nudist section of that Spa were everyone is naked (yes, Europe has lots of those nudist Spa sections)
6. third girl, summer vacation fling, ocean near the beach, underwater, Nice, France, around 4 p.m. in full view of the completely filled beach on a Saturday afternoon
7. fourth girl, german Autobahn at 170 km/h (app. 95 mph) handjob by her and me groping/fondling her around 1 a.m.
8. fifth girl, swinger club, side room, couch. I knew her very well and trusted her absolutely and vice versa. First time anal creampie. Anyone could have passed by. After the act we found out the tissues supplied by the club for that room were empty. I had to escort her to the showers without anyone noticing her dripping cum from her ass and down her legs.

Hell, thinking back I once had a really interesting sex life... hmmm, gotta unship some of those rusty skills

Tie/Toss-up...
In the front seat of a Renault "Le Car", while driving, top down (or back), driving on the highway at 60 m.p.h., OR on the west steps of the capitol building of the 26th State admitted to the Union.