Troy Pilsner, which I've only ever been able to find in Turkey, is my favorite. That opinion, however, may be somewhat effected by experiences had while drinking Troy.

As a side note, unless there are no other options (which, sadly, is commonly the case), don't drink Efes.

At the end of the day, however, I'm more of a Hard Cider person. Woodchuck is my favorite well-distributed brand, and Widmer occasionally puts out a great micro in the Northwest.