More flexibility

The Sass @mixins, and so on...

	@include shake($x, $y, $rot, $name, $steps, $opacity); /* _mixins.scss */ 
	/* 	$x & $y: pixels to move on the X and Y axis,
		$rot: deg to rotate
		$name: the name assigned to those parameters
		$steps: adjust the animation loop (i.e 10 makes an animation in steps of 10%)
		$opacity: true/false to add opacity animation */
	@include shake(40px, 40px, 20deg, 'shake-crazy', 10, true); /* an example */

	@include animation($name, $dur, $iter, $tim, $del); /* _shake.scss */
	/*  $name: animation-name,
		$dur: animation-duration,
		$iter: animation-iteration-count,
		$tim: animation-timing-function,
		$del: animation-delay */
	@include animation(shake-slow, 5s); /* an example */

Attention: you have to use the random() function to compile Sass files.
You could read how to implement it here or here or here.
Remember that there are prefixes on the main code. Hoping that one day we won't need it.
Anyway here is an unprefixed version.