Jack3d is actually my favorite pre-workout formula. Everything else I've tried made me feel like I was on something and the crashes are generally horrible. With Jack3d I actually only take 1 scoop, sometimes 1.5 scoops about 30 minutes before my workout and I'm good to go. Also no crazy crash because I'm not taking too much. Here are the ingredients:
Arginine Alpha-Ketoglutarate, Creatine Monohydrate, Beta Alanine, Caffeine, 1,3-Dimethylamylamine (Geranium [Stem]), Schizandrol A.
It's gluten free with NO FILLERS, and also has AAK and Creatine in it so another reason I dig it. Some folks who take 2-3 scoops say they feel like they just took a bunch of uppers, but that's because of the last 3 components. I admit there hasn't been much research AT ALL on the last two so proceed with caution.
All in all, in moderation, I dig it.