Cut out parts from videos
You can also trim from the middle with QuickTime player, not just from the end. Position the marker at the start of your edit, and do commandY (Split Clip), Then move the red line to the end of the region you want to remove and split it again there. You can now select the mid portion of the video (it should get a yellow border) and delete it. 

See below for the view when you have done both splits, but not yet deleted...