Behemoth Sledge
Artifact — Equipment
Equipped creature gets +2/+2 and has trample and lifelink.
Equip 
Those who worship the great gargantuans could hardly be expected to fight with a subtle weapon.
Steve Prescott
Rulings
Multiple instances of lifelink on the same creature are redundant. If a creature with multiple instances of lifelink deals damage, its controller still only gains life equal to the damage dealt.
(wotc • 2009-10-01)
Rulings
Multiple instances of lifelink on the same creature are redundant. If a creature with multiple instances of lifelink deals damage, its controller still only gains life equal to the damage dealt.
(wotc • 2009-10-01)