There are lots and lots of crappy ones that just pack in the stimulants. Easy to find.
But... Here's my take on a few....
For good quality high-stim products, Insane Labz makes some really good stuff.
Pennywise & I am God are serious shit.... Not for the weak, for sure.
If you're looking (like twoton) for something that gives you some drive without pushing your heart rate thru the roof, Ultimate Orange is the best way to go there. Switches on your focus & no jitters. Pretty low, as far as stimulants like caffeine, etc... It just gets your head in the game.