I would say screen captures. It been built in for years but I don think folks remember they don need an extra program to do it. If you press shiftmand+3 it snaps a photo of the entire screen. Shiftmand+4 turns the cursor into cross hairs and the user clicks holds and drags to create a specific portion of the screen to grab. The runner up would be PDF file format. The Mac is highly adept using and creating the file format without the need for any Adobe products. It extremely useful to be able to use the print menu to create a PDF and Preview as well as Pages can edit them too.