When I first learned how to play a guitar, I was mostly playing power chords really fast. Easiest type of chord to play in a mindless/fast manner.
Initially it was fine if one is into repetitive punk rock or metal type of stuff. (Dunno about other music genres).
If one is into guitar solos played through a lot of distortion, early on I figured how to do all the basic stuff like two-note/three-note hammer-ons, pull-offs, and tapping.
The hardest thing for me initially was learning how to do alternate picking proficiently.
http://en.wikipedia.org/wiki/Alternate_picking