Chest pain
Dyspnea
Subcutaneous emphysema, especially of face, neck, and chest.
Voice change, cough, stridor
"Crunching" sound on auscultation during systole (Hamman's crunch)
Severe cases (generally after trauma) may mimic cardiac tamponade
Pneumomediastinum
Acute coronary syndromes 
Hemothorax
STEMI
Chylothorax
Non-STEMI
Pneumopericardium
Unstable angina