The absolute best beer I ever had, by far, was an ice cold something-or-other in a bottle (I don't even recall what it was, maybe a Mich light or ultra, and I'm sure it wouldn't have mattered) after the long, hot trek out of the Aravaipa Canyon Wilderness following a weekend backpack trip.
Other than that, I spent almost a year working in the UK as a contractor for Det 4 of the 9th SRW at RAF Mildenhall, and did a lot of pub hopping in my spare time. I got spoiled. Pretty much any fresh cask ale over there is awesome. A couple of my favorites: Ind Coope Burton Ale and Adnams Southwold Bitter. Greene King had a good IPA and a Bitter as well.