Hiatal hernia
Alcoholism
Anything that increases intrabdominal pressure: blunt abdominal trauma, CPR, etc.
Classic presentation: Hematemesis following vomiting or retching
As few as 30% of patients present this way
Coffee ground emesis
Melena
Hematochezia
As few as 30% of patients present this way
Mallory-Weiss tear
Peptic ulcer disease 
Esophageal varices
Gastritis/esophagitis
Zenker's diverticulum
Gastric/esophageal varices
Achalasia
Esophageal candidiasis