a busy general practice anesthesiologist. A day can include:
neonates to elderly, neurosurg to ob, regional nerve blocks to cardiac echo, critical care to interventional pain, thoracic to eye balls, general to MAC, pacu to icu to pre-admission clinic to pain clinic.
I'd say rural family medicine hands down. In a really rural area you are ER physician so you see all the ER stuff, plus a bit of everything else. I don't think there is anything that compares to it as far as variety goes, although it's much more time consuming than alot of specialties.