To get loads of gems, (and other items that gives you points only) just turn your back to the object that you are about to destroy, and quickly turn around and hit it.
Take the first barrel on the second level for example.
Walk forth to it, turn your back to it, quickly turn around and then hit it.
This is an old trick that worked on the SNES version too.
Points doesn't mean anything, but still, it's a trick.
Kill with unbreakable punch combos for Guy, Cody
As one may already know, with repeated pressing of the attack button, Guy or Cody hits with a few punches followed by a kick or uppercut to complete the combo and strike the enemy away. Most of the time, the enemy gets up and you have to wait for an open attack to repeat the process.
Not anymore!!! I have found a way of killing an opponent with a chain unbreakable combo that takes all the energy from the enemy without retaliation.
Rapidly tap the attack button non-stop and as soon as the first 3 hits connect, quickly turn and face the other way so that the final uppercut or kick is performed in air, then turn back facing the opponent and repeat the process.
Since right after the opponent is hit, he/she takes time to recover and so by the time you turn round to punch again, there will just be enough time to carry on with the chain.
This is best used for the boss. If done right, you can take out a Boss in under 20 seconds with no damage sustained to yourself.
Subway Warp Technique
In the second ''subway'' level, if you jump on the first barrel and wait there for time to count down, you will be warped to the next section of the game
As you progress through the game you will earn fighting points. These points go towards unlocking secrets in the game itself. If you want to unlock everything you will need 2000 points. Here is the order that the secrets are unlocked:
Extra Lives: This allows you to have 9 lives.
Stage Select: You can choose from level 1 to level 6.
Color Change: Changes character color and unlocks Alpha Guy and Alpha Cody.
Rapid Punch: Now you can simply hold the punch button and you will punch rapidly.