Brettanomyces

With a larger fermentation capacity than most Saccharomyces cerevisiae and S. pastorianus yeasts (except for Brett c.,), they can ferment beers drier and this needs to be taken into account when the beer is packaged. They can produce fruity and funky flavors, and are often used in the production of sour beers. Treat these yeasts with respect, they might need several months to complete fermentation and maturation.