Mac equivalent of Microsoft Paint? (That ISN'T Seashore)

Seashore can't seem to make squares, and when ever I try to make straight lines (by holding shift), the application doesn't seem to paint anything.

I'm a little surprised there isn't anything like Paint that comes with the Mac, it seems like such a simple idea. iPhoto doesn't seem to have any creating features, and is more for editing.

 

Works perfectly, thanks!