the oh crap button
Here's a scenario for you.
You decide to cross that river without checking how deep it is and before you know it the water is lapping over your hood and the engine sucks a bunch of water in through the intake and dies.
This is bad news for most off roaders but not with the oh crap button.
Just put it in 1st or reverse, whichever direction will get you out of the drink.
Hit the oh crap button and start cranking the engine over. Since you're engine just drank half the river it won't start but you can use the starter to get you, ever so slowly, back on to dry land.
That's why the clutch start cancel button is pretty much the coolest thing ever.
Disclaimer : Sometimes doing really cool things with your vehicle is not good for it. (sort of like side stepping the clutch to do really cool burnouts.) Eventual you'll wear out your starter and possibly kill your battery if you use your oh crap button like this alot.