It's hard to beat doodlebug cardstock stickers. They are a great weight so they don't tear if you have to reposition them. And they are repositionable if you move them shortly after placing. They come in all basic colors and lots of font styles so you can use them on practically any layout. And of course, the biggest bonus is the great price!
I am obsessed with the Simply Sweet line by Doodlebug. I have them in all the colors and two sheets of the white and black. (which are almost gone) the font is super cute and clean and they add a tiny bit of dimension and fun to your page.
i really like these stickers, and doodlebug's other alphabet Cardstock Stickers. they come in all kinds of great colors. since they are cardstock (thicker than regular stickers), they add a little touch of 3-D to my projects.