Mine Turtle

When you cast Mine Turtle, you may step on it
and say "Hello" in a high pitched voice. If you do,
sacrifice Mine Turtle and destroy all opponents
creatures and planeswalkers. If you don't, your
opponent can say "Hello", step on Mine Turtle,
and destroy all creatures and planeswalkers at any
time (even if you are in a different game when
they decide to)

"Hello! *BAM!*"
"Well, that's one turtle that I won't step on again!"