One interesting thing about the guitar (and similar stringed instruments like the uke) is that there are so many different ways to play it. You can play with a pick, fingers, or some combination of both. There are also all sorts of relatively new ways to play the guitar in a percussive manner. This post is an overview of all these methods; I will update as I discover more.

Folk style
This is the traditional way people thinking of playing the guitar: strumming chords with a pick. Dylan is a great example.

Classical finger picking
Here no pick is used and the fingers (often the fingernails) do all the work. Take a look at Segovia. (The video takes about 40 seconds to hone in on his hands.)

Pick
The pick is used to play individual notes, often by picking with both down and upstrokes. Who better to showcase this at top speed than Yngwie Malmsteen?

Thumb as a pick
Wes Montgomery is most associated with the technique of using the human thumb in place of a pick. He got amazingly fluid results from such a bulky seeming technique.

Travis picking
Invented by country guitarist Merle Travis, this is a technique that uses the thumb to pluck the bass notes and the other fingers to hit chords and higher melodies. The result is a kind of ragtime piano feel. In this video Travis is using a thumb pick but many players (myself included) Travis pick with no pick.

Van Halen tapping
Eddie Van Halen popularized the idea of tapping notes on the fret board using a combination of fingers from both hands. This interview/demo breaks down the process.

Earlier tapping
As many have noted, Van Halen was not the first to employ this technique (though I believe him when he says he developed it independently of others.) This guy did some great playing in an earlier era.

The Magic Touch
Stanley Jordan took the two hand tapping idea into pianoesque territory. Here he plays two guitars (one being a vibe toned guitar synthesizer.)

More magic touch
Ukrainian guitarist, Enver İzmaylov, combines the magic touch style playing with several other techniques.

Percussive guitar
As well as being an excellent finger picker, Kaki King uses a interesting percussive approach to the guitar.

Slap/percussive guitar
Japanese guitarist Miyavi has a percussive take on guitar reminiscent of funk slap bass.

More percussive guitar
The late guitarist Bob Brozman combined percussive guitar with finger picking and various other flavors.

Flamenco
I’m no expert in Flamenco guitar which is more of a genre of music than a playing technique but I think it’s worth mentioning. Flamenco employs a lot of interesting rhythmic feels and sweeping arpeggios. Paco De Lucia was a master.