I once took a big drink of buttermilk because I thought it was whole milk (which I normally don't drink anyway). I couldn't get that taste out of my mouth all night, it was like spoiled milk sludge. I just physically shuddered a bit thinking about that.
Also, Tequila, not sure why, I'm cool with just about every other spirit, and I drink most neat or rocks, but tequila by itself just makes me wretch. I can drink 151 straight, I'm fine with sambuca (and love ouzo), jaeger, cognac, vodka, etc., but can't deal with Tequila, even smelling it makes me dry heave.