Captain America
Captain America has really improved in his speed department from the previous games. He has a lot of good combos in this one and there is one that can drain almost all of the opponent's life, without a single super. His attack power is good and his defense is also good. If Captain America loses his shield, he becomes faster, but his attack goes down. With his shield, he is able to do better combos since he has a better range and the attack's hit range is better also. He is also stronger. If you want to really speed up, lose the shield. Otherwise, keep the shield.
Special Attacks
Low Shield Slash - QCF+WP
Mid Shield Slash - QCF+WP
Anti-Air Shield Slash - QCF+FP
Downwards Air Shield Slash - (in air)QCF+WP
Straight Air Shield Slash - (in air)QCF+MP
Upwards Air Shield Slash - (in air)QCF+FP
Stars and Stripes - DPM+P
Charging Star - QCF+K
Cartwheel - HCB+P
Super Attacks
Final Justice - QCF+2P
Hyper Charging Star - QCF+2K
Hyper Stars and Stripes - DPM+2P
Combos
D+WK, D+MK, D+FK, QCF+WP
This is a nice 4 hit combo that works only when the opponent doesn't roll away. Use 2 hits into a sweep, then do a low Shield Slash. The shield will hit them for an extra hit, and it will bounce back to. Therefore, you won't lose your shield after this combo.
D+WK, D+MK, FK, DPM+2P
This is a basic super combo that has an odd timing. You just have to use 2 ducking hits, then a standing FK. After that, use the Hyper Stars and Stripes for a next 6-7 hits.
D+WK, D+MK, DPM+2P
This is a weaker variation of the last one, but it is easier to pull off since you don't have the odd timing of the FK in it. Use 2 ducking kicks, then do the Hyper Stars and Stripes right after. This is a painful combo, and should be used whenever you possibly can.
FK, QCF+2P
This is the only Final Justice setup there is. Due to the slow come out time of the FK, this will be hard to set up with. Use a FK, and as soon as it hits them, cancel into the Final Justice. If you time it too early or too late, it won't work though.
FK, QCF+2K
This may be the only setup into the Hyper Charging Stars. Once again, use a FK and then cancel immediately into the Hyper Charging Stars. Once again, if you cancel too late or too early, this combo will not work.
D+WK, D+MK, D+FP, U+WP, WP, WP, U+WP, WK, MP, MK, FP / FK / D+FK
This is a nice long air combo that can do a lot of damage. Most of the times, (the times that the game doesn't cheat you), it will do as much damage as most of his supers. With this combo, use 2 hits into a launcher. Then follow up and use 3 WPs. Then double jump and do a 5 hit combo. Use the FP at the end if you have your shield since it 1) does more damage and 2) it hits more often than the FK. If you don't have your shield then use the FK or the D+FK according to your situation.
D+WK, D+MK, D+FP, U+WP, WP, WP, U+WP, WK, MP, MK, FP, (WP, D+WP, D+MP, D+FP, U+WP, WP, WP, U+WP, WK, MP, MK, FP)
This is an infinite, but you won't have to repeat this more than 3 times before the opponent dies. I know it works on the Playstation version, but I don't know if it works on the Dreamcast of the Arcade yet. For this combo, you need to have your shield. Begin by 2 hits into a launch, then a slow but comboing 3 WPs. After that, you double jump and do the next 5 hits at a normal speed. After the FP, you should be close enough to the ground to WP your opponent off the ground and then do 2 punches into another launcher, then repeating the air combo part. The timing for when you start the air combo changes slightly, but with some practice, you should be able to get it working in no time.