My favorites change all the time, usually something hoppy like a Green Flash West Coast IPA or the IPA included in Sierra Nevada's Beer Camp 12 pack recently which was about $1.50 per bottle. Double Mountain in Hood River makes a nice IRA which is not available in bottles, so I had to brew something.
The great thing about brewing at home is you can create something similar and enjoy 5-10 gallons of that beer for $.20 - $.60 a glass. So in the end the price of commercial beer doesn't mean all that much to me as I usually only buy a bottle at a time in the name of research.