Best Javascript Library

[Aragorn]

I am going to start working on a new project. I have never used any javascript libraries before.
Plz advise me on which is the best javascript library available. Ofcourse, I know that all libraries have pros and cons. My project is not a javascript intensive one. So I needs library that is compact, fast and easy to implement. I don't need much advanced functionalities and features. All comments are welcome :)

[nico_swd]

Personally, I've never used it, but I hear that Prototype (http://www.prototypejs.org/) is very good.

[Aragorn]

But the problem with prototype is that it is too bulky. Has anyone ever tried jQuery?

[Webice]

Prototype is the best. You should also try moo.fx and script.aculo.us for effects.
My friend used jQuery, this is also good.