[evils]

From the top of my head, polyvinylpyrrolidone, lactic acid, bentonite and gypsum are on the permitted list. For beers brewed with top fermenting yeast, sugars and artificial sweeteners are permitted as well (I think they do need to be listed, though).

Note that all of these are used by brewers intentionally, not just as a side-effect. They are used to clarify or to make water more suitable for brewing.