Théoden, King of Rohan

Double strike

Whenever this creature enters or attacks, another target Warrior creature you control gains double strike until end of turn.

First strike

Whenever this creature or another creature you control enters, target creature gets +2/+0 until end of turn.

Whenever Bruse Tarl enters or attacks, target creature you control gains double strike and lifelink until end of turn.

Partner (You can have two commanders if both have partner.)

Constellation — Whenever an enchantment you control enters, this creature gains double strike until end of turn. (It deals both first-strike and regular combat damage.)

Whenever Erkenbrand or another Human you control enters, creatures you control get +1/+0 until end of turn.

Whenever another creature you control enters, this creature gets +1/+0 and gains trample until end of turn. (It can deal excess combat damage to the player or planeswalker it's attacking.)