What will you absolutely never, ever use to make a beer?
For me-
Citra. Tastes and smells like cat piss. Awful stuff.
Ringwood ale yeast: Lazy bitch of a yeast. Floccs too soon, doesn't finish what it starts and leaves your ale tasting like jerky and movie theater popcorn.
Victory/ biscuit: Nothing wrong with them....just every time I use them for a complex malt bill, I end up wishing I had used crystal, amber or something else. It's hard to describe what I don't like about these malts but I just kind of prefer other specialties malts that do the same thing.