This pushup variation by Joe DeFranco is my current favorite:
Pec Poppin Pushups
They are very good for getting time under tension, getting some static internal rotation, and really getting your chest activated. I've found that they are really effective in small numbers, especially for people who are primarily triceps pressers and who need some more chest activation. Since they are bodyweight only and require no gear, you can do them anywhere.
For bench presses who have learned to "pull the bar apart" these might seem to be the opposite - driving the arms together. But in my experience "pull the bar apart" doesn't help my clients and trainees, probably because they don't press with a bench press shirt. Thus, they don't have to train to counteract the pull of the shirt. Instead, getting a chest squeeze to full include the chest along with the deltoids (shoulders) and triceps (arms) on the press is helpful. These pushups really help you feel what it means to have your shoulders tight, arms locked out, and chest squeezing the ground away from you.