Heartless Hidetsugu

{T}: Heartless Hidetsugu deals damage to each player equal to half that player's life total, rounded down.

Fireshrieker

Equipped creature has double strike. (It deals both first-strike and regular combat damage.)
Equip {2} ({2}: Attach to target creature you control. Equip only as a sorcery.)

Dark Sphere

{T}, Sacrifice Dark Sphere: The next time a source of your choice would deal damage to you this turn, prevent half that damage, rounded down.

Pentagram of the Ages

{4}, {T}: The next time a source of your choice would deal damage to you this turn, prevent that damage.

Lightning Mauler

Soulbond (You may pair this creature with another unpaired creature when either enters. They remain paired for as long as you control both of them.)
As long as Lightning Mauler is paired with another creature, both creatures have haste.

Bloodsworn Steward

Flying
Commander creatures you control get +2/+2 and have haste.

Grappling Hook

Equipped creature has double strike.
Whenever equipped creature attacks, you may have target creature block it this turn if able.
Equip {4}

Grafted Exoskeleton

Equipped creature gets +2/+2 and has infect. (It deals damage to creatures in the form of -1/-1 counters and to players in the form of poison counters.)
Whenever Grafted Exoskeleton becomes unattached from a permanent, sacrifice that permanent.
Equip {2}

Loxodon Warhammer

Equipped creature gets +3/+0 and has trample and lifelink.
Equip {3}

Fervor

Creatures you control have haste. (They can attack and {T} as soon as they come under your control.)

Mask of Avacyn

Equipped creature gets +1/+2 and has hexproof. (It can't be the target of spells or abilities your opponents control.)
Equip {3}