cutting off corners on images

I'm desperately trying to figure out how to cut off corners on images in photoshop. This is the closest and most convenient example I could find to explain what I mean:

http://www.melonn.com/images/stafficons/melonn.gif

i've been plugging at photoshop for hours and I can't figure out how to do this. If someone can give me detailed, step-by-step directions on how to do this, I would be so grateful.

PS: I hope this thread hasn't been addressed already ...

!)use the grid in photoshop as a guide....
2)use the polygonal lasso tool to select the corner you wanna cut
3)so the selection will be like

http://www.side-fx.net/temp/selection.gif

then just delete....
hope that helps

It would be much easier to use the Polygonal lasso tool, and make sure to hold down shift while you use it, so that it will lock it into that 45 degree angle.

I would use the regular rectangle marquee tool....

Then transform selection and rotate it 45 degrees and then click the "quick mask" icon on the layers pallet. Done in seconds