The best tasting bar I've ever had without a doubt is Muscletech Meso-Tech cookies & cream, but it's only 27 g protein and 40 or so grams of carbs, not too good when dieting.
A lower carb one that I can tolerate is Pure Protein bars, Blueberry and Strawberry cheesacake aren't bad, S'Mores aren't bad either, one word of advice on Pure Protein bars though, make SURE they are fresh, squeeze the package to make sure the bar is as soft as possible, when Pure Protein bars go stale, they taste like shit.