Wake from sleep
I have had this issue since at least Mavericks and it is still lingering. My MacBook Pro with Retina Display has issues waking from sleep. This isn't always the case, but quite frequently though however. I boot my Mac up in the morning and just sleep it throughout the day as I use it. When I go to open it and wake it from sleep the screen will stay blank and black for a few seconds before waking up, even when trying to hit random keys on the keyboard, or clicking the trackpad, and then it will finally wake up.
MacBook Pro (Retina, 15-inch, Early 2013), OS X Yosemite (10.10.1)