What has had the biggest positive impact on your playing?

carlos

Metronome for every type of practice. Always on, always a pulse to play to. Rhythm choice as important as sound (notes, chords) choice.

Deadman

Not using a single strat anymore (seriously) and using a bit more in the way of effects. I used to do just clean strat all the time thinking I was John Frusciante (mind you his pedalboard in mahoosive) but you (certainly I) can't live like that. Now I'm a tele man and feeling the urge for something Les Paulish and I've never been happier.