D&D4 Wiki
Heavy flail
UZ0503 1 l
Attack bonus if proficient +2
Weapon dice ([W]) 2d6
Type melee
Handedness two-handed
Proficiency category military
Weapon group
Weapon properties
Price 25 gp
Weight 10 lb.

A heavy flail is a military two-handed melee weapon in the flail weapon group.[PH:218][MME:21]

Ardents, avengers, barbarians, battleminds, fighters, paladins, rangers, wardens, and warlords are proficient with all military melee weapons, including the heavy flail.

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