So, you think you might be interested in learning how to play a musical instrument. That's great. It's a skill that you can rely on time and time again for endless hours of enjoyment, and if you're good at what you do then you can even make some cash from it. The important thing to remember when you're choosing your first instrument is what YOU want. It's easy to be swayed by friends, the Internet or even other musicians.
* "My friends all play guitar and I think it'll be a good way to get girls"
Picking up an instrument because your friends play in a band isn't the worst reason to start playing an instrument (it's pretty much why I started) but it isn't the best either. You should start playing because you want to play it, and not because you want to play with your friends. Also, it won't really help you get girls. Learning to play incredible guitar solos won't make you any less socially awkward.
* "I want to be just like Dimebag, I'll rip the **** out of this guitar"
While it's great to be enthusiastic, just remember that it takes quite some time to learn to play an instrument. It's highly unlikely you'll be a solo-god within a year of getting a guitar.
Keeping all this in mind, it's a good idea to consider your favourite type of music and then ask yourself what you really love about that music. Maybe you're into punk and love trashy drums? Maybe you're all about metal and it just has to be a guitar, or maybe you're more about low end grooves and bass. Whatever you decide, it has to be what YOU want.