Okay - here's one for you I have not seen before

You have an image you want to mask - Ctrl (Cmd) + J (twice) to make 2 copies of the intended victim.

Rename the first copy invert and hit Ctrl (cmd) + I to invert the image

Next select the brush tool and select a hard brush - go to brush options and turn down spacing to zero. Hit D on the keyboard to bring up the default colours

Rename the Second Copy 'Mask' and holding down the alt (Opt) Key and click the layer mask Icon at the bottom of the Layers Palette (this should create a layer mask filled with black) now hit 'X' on the keyboard to switch white to the foreground colour and start painting in the parts of the image you want to keep...

When done delete the inverted layer

ctrl Click in the layer mask Icon to select what you just masked and Ctrl (Cmd) + J to promote it to a new level

Cool! Done! If that wasn't the coolest masking technique you ever learned then I'd love to know what was.... and remember where you heard it first!

Tip: If you oveshoot the mask when painting just hit x again to toggle the colours to black doreground and white background and paint back out the parts you don't want