Injecting liquid silicone into the penis can enlarge it very quickly and permanantly, up to 900%. Of course, if you "go too far" you will only be able to use it for peeing and will likely lose sensation in it.
Here are two people that went as far as you can go.
http://www.flurl.com/item/the_perfect_penis_u_100839/
http://www.XTube.com/play_re.php?v=oARMY7YkRen
and then of course there's this guy...
http://web.mac.com/mukhtarsafarov/iWeb/MUKHTARSTAR/Welcome.html
Here are two people that went as far as you can go.
http://www.flurl.com/item/the_perfect_penis_u_100839/
http://www.XTube.com/play_re.php?v=oARMY7YkRen
and then of course there's this guy...
http://web.mac.com/mukhtarsafarov/iWeb/MUKHTARSTAR/Welcome.html