I blew my manager's mind when I told him that if the second controller was plugged in on your NES while playing Duck Hunt on single player, the second controller controlled the duck.
I didn't know that there were continues in Super Mario Bros. You just hold A and press Start on the Game Over screen.
In my office, it's happened more than once....someone wrote on the whiteboard with permanent marker.
You can wipe and spray anything in there, and it's really permanent.
If you take a dry erase marker, and simply scribble over the permanent marker writing, it wipes right off like a dry erase marker.
The knobs on your oven have calibration screws on the back. You can adjust them to get more accurate temperature control and avoid overcooking your dinner.
Shampoo bottles in Japan have dots or ridges on the sides so that they can be distinguished from bottles of conditioner (usually the same size and shape) by touch.
Tape measures have a number of [convenient little tricks](https://www.youtube.com/watch?v=TkoCWUJt10w)
Most caulk guns have a little hole on the handle. Turns out that behind that hole is a small blade that let's you use an unloaded caulking gun to cut off the tip of a new tube of caulk.
I somehow spent 2 years remodeling my entire house before making this realization.
The funny shoulders on [baby onsies](http://thelittleonesboutique.com/wp-content/uploads/2014/07/46.jpg) are there to let you pull the garment down and off so when the kid has a blowout, you don't have to pull it over their head.
My boss is amazed that he doesn't have to use his ipad to take pictures of his phone. He can do a screenshot on his phone.
Sticky keys. My manager broke his arm and one day caught him trying to type with his chin on the shift key. Let him know that's exactly what that annoying pop up was for
The standard iPhone has a level built into it. Go to the Compass app and swipe. Boom, now go fix that crooked painting in the dining room you lazy fuck.
French's Yellow Mustard in the flip top squeeze bottle. Flip open the cap, then continue folding it back until it clicks. No more messy cap.
Edit: Just checked a bottle of Hershey's chocolate syrup and it has one of these mechanisms too.
If you have no network connection on an android phone and try to open a website, it'll take you to a "You are offline" page with a little picture of a dinosaur instead.
What I just learned today, was that if you tap the little dinosaur, it starts a little game where you have to make the dinosaur jump over cactus.