Red Line, without a doubt.. Though you may want to delute it a bit if not use to a shock treatment in liquad form. Can last up to 4-5 hours, so anyone might be warned before taking. Red Bull, RockStar, etc are tame for some, not this stuff. Don' worry, in about 15 minutes,or less, after drinking one you will be ready for a highly intense workout. Surprised it's legal and not sold out the back of a van ,but some health stores will carry it. GNC is one of them. I'm sure when the FDA pay's attention to this stuff, they will take it off the market. Until than, drink up.
A very popular clubbing drink out here in SoCal is Red Bull & Vodka. I would suggest never mixing a Red Line with any form of alcohol. Good Luck.