In Chernobyl, a fungus has been found that feeds on radiation left over from the Chernobyl disaster. This is pretty damned interesting. There's certainly energy there and it's certainly possible, though I wonder if the fungus evolved there or if there's some fungus that simply feeds on a bit of radiation and improved its ability to do so.
In any event, this is pretty useful stuff. Interesting too. Has some survival potential for space even, as there's plenty or radiation in space. What other creatures have this ability? Does the mutation in question have an easy path towards absorbing solar radiation like plants? Plants seem to miss out on the buffet that is green light and if this fungus could evolve that ability, it could wipe out all life on the planet, and that would be awesome (I assume it doesn't leave some O2 as a byproduct). Wait, I'm life on this planet. Hm. Still pretty damned cool.