Theme song from the Good the Bad and the Ugly:

Ukulele Orchestra of GB - The Good the Bad the Ugly

Oh, I remember when I first discovered these guys. What a happy day that was! They're actually really talented musicians, for all they're so humourous! 
I like it best when the whistling guy can't help laughing. 

Oh wow - that was absolutely brilliant!  Thanks for posting that vid.  Excellent!