Not sure if a lot of people know about Cordyceps. It could lead to some pretty sweet mutations on some creatures/NPCs and/or possible risk of infection(HC mode only?) for the player, where they can either try to find a cure or keep it. It could affect player stats, maybe looks, in positive but negative ways(?!)
Radiation + Cordyceps=??
...Although it kills the host in a normal world, anything is possible with radiation!

[img]http://upload.wikimedia.org/wikipedia/commons/8/89/Cordyceps.jpg[/img] [img]http://www.wesleyfleming.com/gallery/ant-w-cordyceps1.jpg[/img][img]http://images.quickblogcast.com/4/6/3/9/3/248966-239364/SpiderCordycepsS.jpg?a=5[/img]


http://www.youtube.com/watch?v=XuKjBIBBAL8 - Video of it affecting Insects.

Mushrooms growing out of my body? Hmmmm, I don't know about ALL that. Unless they were of the magic mushroom sort.