How would you play Magnus

would you play passively or agressively against him

I would use a computer. And I'd probably still blunder.

would he notice?

Depends on which game it is, which Magnus it is, etc.

oh just this Magnus

Magnus meets Magnum:

I would play him using mathematics to guide my moves.  This might help me play more precise moves against him.

Aha!  The mathematical approach.

Hm, I would have to get magnus far more drunk than that to win.

Play a drawish variation forcin him 2 ovakill then blunder.

Ill probably have Ben Stiller seated at my back staring at him with his "magnum look" as we play.

Yeah, when Magnus is faced with my stonewalling...well, you almost have to feel sorry for the guy.

I played a simul against Yuri Shulman (2600+ rating) and trust me, what you want to do against Magnus wouldn't be a consideration. Of course if you're better than me, all bets are off.

I'm guessing even Yuri would be having some trouble against Magnus.

i would resign before the first move XD

Why resign, you may learn something. I'd just do it for the experience. I would obviously be forced to play defensively very quickly.

Could I use my 40,000 volt chess board and wrought iron pieces?  It seems to give me good luck.  

I would invite winnersp along and use the e8 system, confusing him so much he would resign after 10 moves.