There are so many different kinds out there and it can be so overwhelming. I basically go with what Kyle thinks would be best. We also like to stick to brands we know and trust.
First up is N.O.-Xplode by BSN. I have tried the blue raspberry and fruit punch flavors. I prefer the blue raspberry, nice and tangy! When you mix this up you do NOT want to do it with a shaker, the lid can pop off, not that I would know that from personal experience ;) This stuff kicks in right away for me, I get tingly all over and am ready to work out and I get really vascular! Sometimes it is a bit much for me, but I do like this product.
For the final pre-workout we have Pump Igniter by Top Secret Nutrition. I first decided to try out this brand for their protein (which is amazing) thanks to a gal I am friends with on bb.com, Kristine Loock, she is one of their sponsored athletes. The Pump Igniter happens to come in my FAVORITE flavor of all time, cherry limeade :) The flavor is phenomenal, the intensity is right in the middle of the intensity I would get from the N.O.-Xplode and the Assault. I didn't notice any increase to my vascularity but I do feel like it helped push me more through my workout.
In the end I have to say that I LOVE each of these pre-workout products, I will change up what I use every couple of weeks and continue to purchase each of them. They each give me something a little different which makes me feel like I just can't choose a favorite.
Regardless of what you like to use I really do feel that using these products helps me get through my heavy lifting and pushes me past my limits. I can really tell a huge difference when I workout without taking one of these!