Bring up the keyboard anywhere

There are essentially two ways to do that, one discovered/reported by Reck, other one by me.

My way: If you hold down the Steam-Key (The glowing one in the middle with the logo on it, obviously) and then press the button left of it (aka the select key, or the back key, it has a triangle pointing to the left on it) the keyboard opens. However, the action bound to that key will still occur, so don't bind something like "close chat" to it, otherwise it will first close the chat and then open the keyboard.

This does only work while in a game, if you are on the desktop pressing the steam key just opens Big Picture mode.

Reck's way: With Big Picture mode minimized, click the left stick (push it in, so it clicks, don't tilt it) to open up a window with the keyboard in it. In an answer to Smirking Wolf's question, Balderick mentioned you can then move the keyboard to another place by pressing X, however it just snaps between those two places.

Accurate Aiming

This was first suggested to me by A.K.A. The Boss, but I kinda ignored it until a huge steam info thingy popped up on my screen showcasing this feature/trick.

If you have your right trackpad set as a mouse, you can pump the sensitivity up to allow quick fast turns. Then, you go to the gyro sensor (The little atom/sphere/circle symbol under the middle) and set it to activate "on right pad touch", and set it to mouse with a medium to low sensitivity.

That way, when you put your thumb on the right trackpad to look around, you can turn around very quickly by moving your finger, and aim precisely by tilting the controller.

Turn the turbo function on/off

If you want to have buttons that don't always rapidly fire, but still occasionly have to, just Mode-Shift and do the exact same bindings, but this time, enable/disable the turbo function.

It works best with the triggers, when you set the shifting key to "Left/Right Trigger Full Pull" and then activate the turbo feature, that way you can softly pull the trigger for one click and completely pull it in to spam that (or another) key!

This can be useful in games like Nidhogg, where you have basically two types of movement, depending on if you hold down the movement key or spam it. If you don't want to break your fingers and or the controller, then do that method, so you can just hold down something to spam the key.

Some useful key combinations (contributed by Balderick in this post)

X + Steam: Pair controller to device

A + Steam (when controller is off to power on): Cycle through pairing options (Like Computers, or Steam Links)

Steam + Right Trigger: Screenshot

Steam short press: Switch controller on / Steam overlay / Open Big Picture

Steam long press: Switch controller off

Steam + Y: Detailed streaming stats

To be continued...

I will try to keep this guide up to date, either when I find out something new, or I remember to read the comments, so feel free to write your discoveries (if anyone ever reads this guide, because it's kinda hard to find).