If you can consider it a technique, I'd say speed. I'll never be a shredder like Vai, Satriani, or Eddie Van Halen, but I'd love to be able to play some of the speed runs you hear in blues, like SRV, Clapton, Eric Johnson, and even Gilmour.

I know what I need to do to build it up...I just need to do it. By accident of learning more songs and just playing regularly, my speed and accuracy has increased. It's a constant challenge - it seems like you can never be fast enough :-).

Phrasing is another one. I've made great strides with this one (thanks Anders!!), but it is another constant challenge.