Notes from a sensory training class I took at my LHBS. We tasted beer with these flavors enhanced in them. Definitely a useful learning experience!
Acetaldehyde: green apple; National Bohemian; Budweiser.
Isoamyl acetate: estery, fruity, bananas; Schneider Weisse, Leffe
Dimethylsulfide: Cooked vegetables, corn, celery, cabbage; rolling rock; perception of crispness (all sulfurs)
Diacetyl: butter, butter popcorn; not slickness (misconception); Newcastle, red hook, shipyard, most British beers.
T-2-N: paper, cardboard, stale; from oxidation; sherry-like, barleywines, old ales;
Infected: diacetyl, sour, all the above; dirty tap lines, contaminated beer.
Spicy phenols, chlorophenol, 4-vinyl guaiacol: spices, cloves, bandaid (in high amounts); over chlorinated water, smoky phenols, yeast strain dependent;
Isovaleric acid: stale cheese, sweat socks, putrid; oxidation of free fatty acids; old poorly stored light struck hops;
Butyric acid: rancid, baby vomit, putrid; anaerobic spore-forming bacteria; poor wort sanitation, dirty heat exchanger, sugar solution spoilage (not boiled long enough).