For me the UK-style bitter is the perfect beer. Pungent, earthy hop aroma that is still understated, rich malt aromas, and fruity yeast esters all combining to make a perfectly balanced session beer that packs a lot more flavor into a "smaller" beer. If I could have but one beer for the rest of my life, this'd be it.
Honorable mentions include homebrewed pilsner, IPA and its very interesting spawn Tripel IPA, rauchbier, and the "middle of the road" stouts in the FES and double stout class.