Lich

[Deathseide]

Ok, so would I lose the game if I {donate} a {lich} to my opponant and then destroy it? Or would my opponant?

[Imdowd80]

yes, because your life total would be zero,

RESOLVED

[Seth5000]

You lose because you lost control of it before your oponent

[Wally]

Ok, so would I lose the game if I {donate} a {lich} to my opponant and then destroy it? Or would my opponant?

Let say you had another way to stay alive with 0 life so we can actually answer your question more thoroughly.
Eg.  {Platinum Angel},  {Phyrexian Unlife},  {Lich's Mirror}, etc.

Now you have kindly {Donate}d the {Lich} that entered the battlefield under your control to your unworthy opponent.

So, what happens?
Your opponent's life total wont change, as that was only an enter the battlefield trigger, and well, he just swapped teams.

Now if by some way he died (goes to the graveyard from the battlefield) then his other ability triggers. Killing "you"

What's interesting is now that "you" refers to its controller and not it's owner.
Hence your opponent loses the game.