Parks, hiking, public washrooms... Work - but that's landscaping and construction, so outside more or less. I guess driving counts, or usually pulled over at the side of the road somewhere. Parked along the beach with cars fairly close by..
But over all, not actually waving my cock around in 'public'. Though for sure in some washrooms guys are checking you out, and sometimes leads to more.
And I guess gay bars and clubs, general showing off.
The beach right next to me, mid-week around dinner time is dead. Nice to go down with a couple beers, sit on a log, and sometimes wank. Really nice. Keep half an eye out in case someone is actually walking along the beach.
On my motorbike a couple times.