Lightning Skelemental

Trample, haste
Whenever this creature deals combat damage to a player, that player discards two cards.
At the beginning of the end step, sacrifice this creature.

Ball Lightning

Trample (This creature can deal excess combat damage to the player or planeswalker it's attacking.)
Haste (This creature can attack and {T} as soon as it comes under your control.)
At the beginning of the end step, sacrifice this creature.

Thunderkin Awakener

Haste
Whenever this creature attacks, choose target Elemental creature card in your graveyard with toughness less than this creature's toughness. Return that card to the battlefield tapped and attacking. Sacrifice it at the beginning of the next end step.

Spark Trooper

Trample, lifelink, haste
At the beginning of the end step, sacrifice this creature.