Shaco is an extremely feared champion beacuse of his stealth and backstab abilities, but there is another ability that most of the people actually dont really know how to use and its called
Jack in the box.
This little box might not deal a great amount of damage (unles you build an AP Shaco) but man it does help you alot if used well.
Lets say you are already in mid game.. and for some reason you find yourself pushing one lane alone,you know that you are gonna get ganked sometime, so a good way to avoid this.. is as you push foward through that lane, always make sure you put a box in everysingle path or route that the enemies might cut through to surprise you.if you want to push that lane hard. make sure you have from 3 to 5 boxes covering all those routes and strategic spots.. so not only you see when the enemy is coming but it fears him away for a second, and a second in a squishy champion like shaco is more than enough to make your epic escape and leaving them bare handed.
another good use for the box is when you are chasing an enemy very close but not so close for an autoattack and you might think you will not get him before he gets to a tower.. well the the box can help you here also. the ability does have a small range of placement. so while chasing the foe, you can place a box infront of him, making him fear and stepback for 1 sec (1.75 when ability maxed) and in some cases that second is more than enough for you to crit him to death.
And last but not least , you can use the box for some few things including:
Jungle - it helps with the neutrals
Lane bushes - placing one on early game lane bushes helps you avoid some surprises jumps or flashes
Towers - when hiting the tower, run pass it a bit and place a box to delay any incoming enemies
Escaping - when escaping with the enemies chasing.. place a box as you run and hope the enemy gets feared away.
Do not place a box when the creeps are fighting each other and you have a range hero enemy in sight distance, he will destroy your box as soon as you place it. You need to place your boxes when the others are out of sight.. so it gets them by surprise.