Here I present recent research in our lab characterizing evolution in three types of fungal parasites: obligate specialist parasites highly adapted to their hosts, generalist parasites which choose a parasitic lifestyle but maintain saprotrophic abilities, and opportunistic parasites which appear to evolve from selection on diverse saprotrophic ability. First, I describe the phylogeny of a novel group of obligate endoparasites, the Cryptomycota which places a parasitic root on the fungal tree of life. Then I describe our population genetic work on the amphibian killing chytrid, where population genetics identifies a potent killer strain of unknown geographic origin. Finally, I will touch on experimental approaches to characterize the genetics of virulence by forcing brewers yeast to behave pathogenically. All fungi have the capacity to be killers, because they digest the world around them.