Continuity mistake: In the bar gunfight scene (where Cheech is the barkeep), Banderas and the bookie from the back room end up on the bar with pistols pointed at each other. Banderas puts his weapon down, then two camera cuts later he puts it down again.
Continuity mistake: During the shootout at the Tarasco bar scene, there is a part where El Mariachi is shooting bad guys from the front of the bar. He switches from sitting to lying almost face down throughout the scene.
Answer: It is called "Pass The Hatchet", and it is written by Ray Theriot, Roger Leon Jr. & Earl Stanley Oropeza. It was performed by Roger & The Gypsies. If you buy the soundtrack CD, it is on there, too.
Deezul