Bear Grylls did a frontal nude sequence for "Man Vs. Wild" --- but sadly, it was optically fogged in the genital area by the Discovery Channel.
Nevertheless, you can still see quite a bit:
--- and you can see more still (in terms of 'movement'
behind the optically fogged area) in the 30-second clip of video
from which I took the above caps:
Badongo One Click Web hosting
[video will start playing on-screen after between 10 and 60 seconds, depending on your connection speed]
And here are a couple of other sexy shirtless images: