Are you ready to play the unofficial "most cool instrument in the world"? Well, yeh, that's the guitar. Yes, playing guitar is cool. Some people miss out on it, though - but they'll look back later with remorse and say: "i studied classical piano when i could've been playing guitar..."
But since you've decided to learn guitar, I'd like to give you a few pointers to get you started.
First of all, if you're serious, get a decent instrument. Don't pick up a $50 guitar from Walmart. At least invest in a name brand beginner's guitar. I bought an Oscar Schmidt acoustic guitar from a friend for $90. A price like that sure didn't break the bank, but it's a quite decent guitar, especially for someone like me - my expertise is on the keyboard, not the guitar.
Secondly, get some help learning guitar. If you're pretty musical, you might get by with a DVD or instruction book teaching you how to play. Or, you may have a friend who can help you out a little. Most of us, though, will learn guitar quicker with a teacher. Find a teacher that is a good guitarist, but is also a good teacher. Also, be sure that they play the type of guitar music you want to learn. For example, if you want to play rock music, don't get a classical guitarist for a teacher!
Thirdly, learn guitar by playing songs that you love. It's much more fun to practice when you're playing your favorite songs. The great thing about contemporary guitar music is that no matter how much of a beginner you are, you can find great songs to learn. If you're really new, you might even want to try one of the old "three chord" rock songs, by the likes of Elvis.
Of course, one of the most important things you should do is practice!