title_body: What beer is really bitter, but has a fantastic aftertaste?
upvoted_answer: For really bitter, a double/imperial IPA is the way to go. For the big bitter hop flavors, check out some of these: Stone Ruination IPA, Port Mongo IPA, Russian River Pliny the Elder, Lagunitas (pretty much any of their hoppy beers), Southern Tier 2XIPA, Cigar City Jai Alai. Many more to choose from depending on your location. Maine Beer Company and Kane Brewing are two of my favorite small breweries on the east coast.
  
  As Pepi mentioned, sour beers are certainly very interesting. A great start into the world of sours would be the Oud Bruins -> Monks Flemish Sour Ale, Rodenbach Grand Cru, or Liefman's Goudenband. These will run your a little more $$ but are super refreshing and really great to sip on. They open up and change flavor that longer you leave them out.
  
  Cheers.