Poll Results

Total votes: 2658

Walking: 700 (26.3%)
Cycling: 557 (21.0%)
Falling: 275 (10.3%)
Swimming: 209 (7.9%)
Brachiating: 201 (7.6%)
Gliding: 137 (5.2%)
Skiing: 131 (4.9%)
Rowing/Paddling: 73 (2.7%)
Running: 64 (2.4%)
Climbing: 61 (2.3%)
Skating: 61 (2.3%)
Diving: 40 (1.5%)
Whitewater rowing: 40 (1.5%)
Crawling: 30 (1.1%)
Push-scootering: 26 (1.0%)
Jogging: 19 (0.7%)
Skateboarding: 19 (0.7%)
Surfing: 15 (0.6%)

A few people nominated sailing, which I would have included if I'd remembered it when compiling the question. And I realise these all require some sort of power source - by "unpowered" I meant without an animal or mechanical engine.