Secret features which enhance the user experience

OK, I have to admit they are not strictly secret like so called Easter Eggs, features hidden in widely used software, which the programmers think are great fun but which some of us think are a waste of our computing resources.  

One notorious example was the Flight Simulator built into Excel97. Microsoft apparently banned the practice in later years as part of its trustworthy and openness initiative but they are still quite common. 

No, I am talking about very useful features, which many people do not seem to know and which do not appear to be widely publicised.

Showing a blank screen before or during a PowerPoint presentation

I still see lots of people inserting blank slides manually into presentations. This means that you have to put them in before you run the slideshow and are then stuck with what you have there. 

An extremely useful feature is to press the 'w' key at any time during a slide show, which will then give you a white blank slide. To return to the slideshow, simply press 'w' again. 

For a black blank screen, do the same with the 'b' key. It is shown as a keyboard shortcut in help but it's so useful, I don't know why it isn't better known.

Taking a screen shot on an iPhone or iPad

Again, this is a very useful feature. All you need to do is press the home button and the power button at the same time. This takes a photo of the current screen, which is then available in your photo app for editing and use. 

I use this all the time, often just to temporarily keep track of a webpage. I find it especially useful for transaction and discount codes which you might need when the internet is not available. 

Simply showing the screen shot in a restaurant is much easier than finding the relevant email in your inbox, particularly when you have received lots of emails since getting the code.

Undo on an iPhone or iPad

L'esprit de l'escalier was coined in the 18th century to describe the phenomenon where we think of the perfect witty reply just slightly too late ie on the staircase when leaving the salon. 

In a similar vein, we often realise we have made a mistake just after pressing 'enter' or 'delete'. The undo function is a lifeline for many of us but I only found out recently that iPhones and iPads have an undo function on many apps. 

All you have to do is shake the device and an undo screen appears. Although the option is to 'undo typing' it also works for deleting.  

I am sure there are many more similar features which are also much less well known than they deserve.  Maybe you can suggest some?

I guess one reason why features are not well known is that many of us never read manuals and tend to 'limp along' in our use of gadgets and programs once we have mastered the basics. 

Indeed, I understand that when software developers offer a wish list for new features in their products, many of the suggestions already exist in the current version - which says something about the usability of the software but also perhaps of our unwillingness to invest in learning new tools properly.

This could be an opportunity for 'smart' tips which are only revealed when your use of a program reaches some level of confidence.  However, I generally find 'tips' in such progams fairly unhelpful and I certainly don't want a return to the irritating Microsoft paperclip character telling me that it thinks I am writing a letter and it would love to help!

So has anyone got a solution?