The only time you see a McLaren F1 without an engine these days is if someone crashed it into a tree and it got ripped in half. Jay Leno just took the engine out of his car for a service. It's the most nerve-wracking thing ever done in the Big Dog Garage. Fair warning: This video is nearly porn.
The BMW V12 in the McLaren F1 is basically the archetype for engineering porn when it's in the engine bay. Take it out, and you're seeing one of the wonders of the engineering world like you've never seen it before.
Just look at it. Even if you aren't into looking at an engine, I think that'll change when you look at this. The sight of those headers is enough to make me weak in the knees.
(Hat Tip to Scott!)