My favourite:
http://joesnyder.co.uk/index.php/thongs/thong/medium/joe-snyder-thong-turquoise-m.html
Why? Because it feels better than silk and cups my penis very well. Its a little expensive but trust me its worth it.
I used to wear female thongs because a while back mens thongs all just seemed to be silly novelty thongs. Its 80% Nylon 20% Spandex Lycra, couldent be better :)
Also I like the below because it looks good and actually looks masculine which is really hard to archive with most thongs. It doesnt feel as good as the above but looks the best.
http://www.hisroom.com/clever-1004a-izmir-thong.shtml