Taking L-Arginine does increase blood flow to tissue, particularly erectile tissue. But its an excellent way to get a cold-sore re-currence if you have had one before. Just thought I'd add that.
Anyway, the stuff aimed at increasing sexual performance and sensation and also now the stuff designed to make you do spectacular 'cum shots' (like Peter North) are quite interesting. I was looking at this stuff 'Maximum Pills' and its got some great stuff in it.
You could use this stuff down the gym, I broke down the ingredients and figured how each bit could have bodybuilding usage. Erm, the Zinc looks useful and Horny Goat weed, but depends what you are going to actually do down the gym workout or have sex ?