Cardiac
Inferior MI (involving RCA)
Sick sinus syndrome
Neurocardiogenic/reflex-mediated
Increased ICP
Vasovagal reflex
Hypersensitive carotid sinus syndrome
Intra-abdominal hemorrhage (i.e. ruptured ectopic)
Metabolic/endocrine/environmental
Hyperkalemia
Hypothermia (Osborn waves on ECG)
Hypothyroidism
Myxedema coma
Hypoglycemia (neonates)
Toxicologic
B-blocker
Ca-channel blocker<unk> 
Opioids
Organophosphates
Ethanol
Clonidine
Infectious/Postinfectious
Chagas disease
Lyme disease
Syphilis
Other
Brash syndrome
Inferior MI (involving RCA)
Sick sinus syndrome
Increased ICP
Vasovagal reflex
Hypersensitive carotid sinus syndrome
Intra-abdominal hemorrhage (i.e. ruptured ectopic)
Hyperkalemia
Hypothermia (Osborn waves on ECG)
Hypothyroidism
Myxedema coma
Hypoglycemia (neonates)
Myxedema coma
B-blocker
Ca-channel blocker<unk> 
Opioids
Organophosphates
Ethanol
Clonidine
Chagas disease
Lyme disease
Syphilis
Brash syndrome
Assume any wide-complex tachycardia is ventricular tachycardia until proven otherwise (it is safer to incorrectly assume a ventricular dysrhythmia than supraventricular tachycardia with abberancy)
Regular
Monomorphic ventricular tachycardia
PSVT with aberrant conduction:
PSVT with bundle branch block^
PSVT with accessory pathway
Atrial flutter with bundle branch block^
Sinus tachycardia with bundle branch block^
Accelerated idioventricular rhythm (consider if less than or ~120 bpm)
Metabolic
Hyperkalemia<unk> 
Severe metabolic acidosis
Irregular
Atrial fibrillation/atrial flutter with variable AV conduction AND bundle branch block^
Atrial fibrillation/atrial flutter with variable AV conduction AND accessory pathway (e.g. WPW)
Atrial fibrillation + hyperkalemia
Polymorphic ventricular tachycardia
Torsades de pointes
Nonsustained ventricular tachycardia
Monomorphic ventricular tachycardia
PSVT with aberrant conduction:
PSVT with bundle branch block^
PSVT with accessory pathway
Atrial flutter with bundle branch block^
Sinus tachycardia with bundle branch block^
Accelerated idioventricular rhythm (consider if less than or ~120 bpm)
Metabolic
Hyperkalemia<unk> 
Severe metabolic acidosis
PSVT with bundle branch block^
PSVT with accessory pathway
Atrial flutter with bundle branch block^
Hyperkalemia<unk> 
Severe metabolic acidosis
Atrial fibrillation/atrial flutter with variable AV conduction AND bundle branch block^
Atrial fibrillation/atrial flutter with variable AV conduction AND accessory pathway (e.g. WPW)
Atrial fibrillation + hyperkalemia
Polymorphic ventricular tachycardia
Torsades de pointes
Nonsustained ventricular tachycardia
Torsades de pointes
Nonsustained ventricular tachycardia
^Fixed or rate-related
Digoxin toxicity
Cardiac
Beta-blocker toxicity
Inferior MI 
Amiodarone pulmonary toxicity
Sick sinus syndrome
Clonidine toxicity
Neurocardiogenic/reflex-mediated