I'm thinking of getting a bike for exercise, i'm 15, should i get one??? What brand??

It will have to look pretty decent.

Find a local bike shop. Go in and tell them about how much you want to spend and where you'll be doing most of your riding. They should be able to help you. And make sure it fits.

I bought this bike for my Daughter:

<>http://i134.photobucket.com/albums/q119/...

<a href="http://s134.photobucket.com/albums... target="_blank"><img src="http://i134.photobucket.com/albums/... border="0" alt="Fuji Blvd 2"></a>

It's a Fuji Boulevard, 21 speed Ladies Mountain bike. The handlebars were replaced with BMX bars. It has LED headlights and tailights.
This bike was $279.00 before the accessories.

How it performs is more important than how it looks.

Absolutely - get one. Get the brand you like, it's a free country, right?

Spend the money on joining a gym! You can use their stationary bikes, a lot safer than going on the road, plus all the other exercise equipment, and you will get to meet lots of new friends.

Badco.

Yes, get a bike. Riding burns as much calories as running over time, a staggering 350-500 KCal/hr.

I don't advise spending more than $350 for your first bike, however much you actually have to spend. You'll see plenty of fine-looking bikes at this range, in all the major styles (I'm talking about road, mountain, and hybrid).

I'll also say try to spend as close to that limit as you can, because at this range, you're getting a whole lot more quality for a price bump as small as $20.

Make sure you buy from a bike shop that tries to help you pick a bike to fit your body. They should do things like study your posture as you sit in riding position. The really nice shops bring out special instruments for this purpose. 15-year olds are sometimes shaped a little funny, so be ready to switch out parts to fit, and switch again as you grow. This is important because a bad fit can lead to all kinds of stress injuries.

I emphasize buying from a bike shop, if you can help it. It might cost a little more than Wal-Mart, but they will also help you maintain your bicycle at a reduced cost or none at all.

Wal-Mart clerks will just look at you funny if you bring it back when the brakes stop working. They won't care if it doesn't fit either.

i like bmx

any mountain bike that you like the design of or a penny farthing.

Get any one on sale from a reputable store in a colour you really like. It'll be cool!