Ball Lightning

Oracle Text

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 Ball Lightning.

Card Rulings

2/1/2007 The creature is sacrificed at the end of every turn in which it is on the battlefield. There is no choice about what turn to sacrifice it.