Vibrato (Whole Arm Style)
I managed to ignore this technique for the first 15 years I played guitar, man I wish I hadn't, it's really cool. Not I've got it down I use it as much or more than the standard 'pivot' vibrato.
If you are new to it I'd recommend starting with just 5 minutes a day for a few weeks to get let the muscles develop, starting in slowly and getting the technique solid. Get it into you muscle memory and then you'll just find yourself using it naturally. Might want to start on string 2 and only get into the thinnest string when you have mastered it on the others cos it is a lot harder!
You can clearly see Clapton using this technique on this video at 1:14 (thank Kris!)