I'll chime in another vote for Sin City's hefeweizen. I don't think much of their other beers but the hefeweizen is very good. During summer months they often run deals for two 32oz pitches for $15. Sometimes it's two pitchers plus two shots of whiskey for $25. You're most likely to get the best deal going to Sin City in The Flamingo because they always seem to run one of the specials but the other stations don't always seem to advertise it.
Burger Bar is fine but you can catch all of those beers plus a lot more by going a little north into Monte Carlo at The Pub. (Burger Bar has better burgers but The Pub's beer selection is far larger.) It's definitely the place to go to try the most beers but not necessarily the most exotic.
I have recently come to love Public House in The Venetian. They always have sour beer on tap and casks, plus a good mix of beers. Some of the stuff is the same that other beer bars have on tap but they have a few things that you won't find elsewhere on the strip. Don't ignore the bottles and cans. Some good stuff in there.
Surprisingly, Ramsay's Burgr in The Miracle Mile also has a decent selection at very reasonable prices for Vegas. They carry a good mix of beer including one or two barrel-aged Innis & Gunn (the stout is not cloying like the standard barleywine/whatever beer) because Ramsay's restaurant business has some connection with them. Plus, the burgers here are incredible. Way better than burger bar but not your usual 100% ground beef burgers. The beef is a combination of some high end ground beef, brisket and I think short rib.
Ellis Island, right behind the strip, has a brewpub inside and is supposed to be decent beer at very cheap prices.