I imagine motor oil gun smoke cigar smoke metal ( if you've ever run your hand down a metal railing and they for reason smelt your hand that smell ) and a gorilla and a hint of mushroom and a blood can't forget blood smell
coming soon to a mall near you "WWWAAAAAAAAAAAAAGGGGGGGGGGGHHHHHHHHHH, by Kelvin Kline" then we can all get a wiff.
For some real-life references to stinky fungi--some of you Elder Scrolls fans might recognize the Stinkhorn: http://www.clemson.edu/extension/hgic/hot_topics/2008/11stinkhorns.html Excerpt: The fact that Stinkhorns smell as bad as they do in order to attract Nurgle-Loving flies and beetles helps in the "smells akin/worse than a plaguebearer". Note that Orks exude spores all the time, so--unlike the brief stint of stinkhorn stink--Orks could smell like fecal-death ALL THE TIME! So I'd imagine "Ork Smell" as Stinkhorn-on-Steroids on top of grot-oil (petrol) & boom-powda (gunpowder). Overall, I'd say that's a uniquely rank odor. EDIT: The Stinkhorn's spore mass is described as-- --that sounds pretty Orky to me too!
My Codex sums up the smell of Orks in one sentence. "More offensive still is the Ork's smell, which has been likened to a diseased Grox languishing in its own dung." And that's in addition to motor oil, and whatever else the Ork's dirtied itself with
Probably pretty earthy-plantish, with some agressive mixture of poisonous spores and lots of sweat, rotting meat and rusty metal out of the mouth with mushroom-beer and squigmeat flavoured blurps. And that is the Ork by himself, without the stuff he has sticking on his body
