Back when I was drinkin them it was Monster for me. I've tried Amp, rockstar, Red Bull and I'll say that Red Bull tasted the worst out of them all. Amp tasted pretty good but it kinda felt like I was drinking soda. Rockstar was nasty as well. Although I will say that the coffee that I fix up is sure to give you jitters cause I jack it up with sugar.
But Monster gets my vote.