I actually write a lot of parody fanfiction. My latest Trigun related one is sort of a crossover between Trigun and The Legend of Zelda: The Windwaker. It's main focus is humor, and as such, it's not very well written and doesn't have any logic whatsoever, but I decided to post it here because it's my best written one, though it's not that great. If you're expecting seriousness, plot, length, and big words (Well maybe I'm wrong about that one, the first chapter has the world's longest word, Pneumonoultramicroscopicsilicovolcanoconiosis and the second longest word, antidisestablishmentarianism in it) it's not for you. If you want randomness, cheap laughs, something easy to get into, and you also happen to be a Legend of Zelda fan, this one's for you!
Here it is:
http://www.fanfiction.net/s/4647627/1/The_Gunsmoke_SeaMy second best Trigun related one is Homestar Gunner. It's probably the strangest crossover ever. Even more so than Final Fantasy and Disney. (Yeah, I went there!). Same message as the above, minus the big words and Legend of Zelda part. This one might be even more random and stupid than The Gunsmoke Sea ALSO, WARNING: THE EARLY CHAPTERS ARE VERY BAD! Just skip to chapter 9 and read on. Chapter 2 was improved later after I wrote it, and a lot of it is pretty funny, I still think some of the jokes were kinda stupid, even more so than normal, as in the bad kind of stupid, and not the random and insane kind of stupid I like. I recommend visiting homestarrunner.com first, so you know the characters.