Blade II 2M - I know this is the third nomination for one of these but they really are that good. Besides if I did sell it who knows if I'd be able to get another -they're extremely hard to come by...
At the other end of the spectrum it would be a wrench to get rid of my B III 8.5, things would need to be really bad.
And then again, the 4.9...and the 3.3...and the Trampa...no, I'd have to keep the lot:D