Actinomycosis is a rare, chronic disease caused by a group of anaerobic Gram-positive bacteria that normally colonize the mouth, colon, and urogenital tract. Infection involving the cervicofacial area is the most common clinical presentation, followed by pelvic region and thoracic involvement. Due to its propensity to mimic many other diseases and its wide variety of symptoms, clinicians should be aware of its multiple presentations and its ability to be a 'great pretender'. We describe herein three cases of unusual presentation: an inferior caval vein syndrome, an acute cholecystitis, and an acute cardiac tamponade. We review the literature on its epidemiology, clinical presentation, diagnosis, treatment, and prognosis.