Generally speaking, all pre-workout supplements contain the following ingredients...
Beta-Alanine - Reduces the lactic acid build up in your muscles
Arginine - A non-essential amino acid which causes vascular dilation allowing for more nutrients to be passed to your muscles. This prolongs training by improving muscular endurance and delay muscle fatigue
Caffeine - Central Nervous System stimulant which increase mental and physical activity
Creatine - A nitrogenous organic acid which enhances energy production to all cells in the body. It is particularly useful in explosive muscle contractions during anaerobic exercises.
Here are the top 5 supplements that I have encountered so far:
1. C4 - Cellucor
2. NO-Xpode - BSN
3. Jack3d - USPlabs
4. 1.M.R - BPI