D&D4 Wiki
Attack bonus if proficient +2
Weapon dice ([W]) 2d4
Type melee
Handedness two-handed
Proficiency category simple
Weapon group
Weapon properties
Price 1 gp
Weight 10 lb.

A greatclub is a simple two-handed melee weapon in the mace weapon group.[PH:218]

Ardents, artificers, avengers, barbarians, bards, battleminds, clerics, druids, fighters, invokers, paladins, psions, rangers, runepriests, seekers, shamans, sorcerers, swordmages, vampires, wardens, warlocks, and warlords are proficient with all simple melee weapons, including the greatclub.

Other classes do not have proficiency with the greatclub as a class trait, but any character can become proficient by taking a Weapon Proficiency feat.