[animate.css](http://daneden.me/animate/) extension: `popAndBounce`. This one is intended to be repeated.

popAndBounce.css

@-webkit-keyframes popAndBounce {
	0%, 40% {
		-webkit-transform: scale(1);
	}
	5% {
		-webkit-transform: scale(0.9);
		opacity: 0.7;
	}
	10%, 15%, 28%, 35% {
		-webkit-transform: scale(1.2) translateX(0);
		opacity: 1;
	}
	20%, 24% {
		-webkit-transform: scale(1.2) translateX(-20px);
	}
	22%, 26% {
		-webkit-transform: scale(1.2) translateX(20px);
	}
}

@-moz-keyframes popAndBounce {
	0%, 40% {
		-moz-transform: scale(1);
	}
	5% {
		-moz-transform: scale(0.9);
		opacity: 0.7;
	}
	10%, 15%, 28%, 35% {
		-moz-transform: scale(1.2) translateX(0);
		opacity: 1;
	}
	20%, 24% {
		-moz-transform: scale(1.2) translateX(-20px);
	}
	22%, 26% {
		-moz-transform: scale(1.2) translateX(20px);
	}
}

@-o-keyframes popAndBounce {
	0%, 40% {
		-o-transform: scale(1);
	}
	5% {
		-o-transform: scale(0.9);
		opacity: 0.7;
	}
	10%, 15%, 28%, 35% {
		-o-transform: scale(1.2) translateX(0);
		opacity: 1;
	}
	20%, 24% {
		-o-transform: scale(1.2) translateX(-20px);
	}
	22%, 26% {
		-o-transform: scale(1.2) translateX(20px);
	}
}

@keyframes popAndBounce {
	0%, 40% {
		transform: scale(1);
	}
	5% {
		transform: scale(0.9);
		opacity: 0.7;
	}
	10%, 15%, 28%, 35% {
		transform: scale(1.2) translateX(0);
		opacity: 1;
	}
	20%, 24% {
		transform: scale(1.2) translateX(-20px);
	}
	22%, 26% {
		transform: scale(1.2) translateX(20px);
	}
}

.popAndBounce {
	-webkit-animation-name: popAndBounce;
	-moz-animation-name: popAndBounce;
	-o-animation-name: popAndBounce;
	animation-name: popAndBounce;
}

usage.scss

.rejected {
	@include vendor(animation-name, popAndBounce);
	@include vendor(animation-iteration-count, infinite);
	@include vendor(animation-duration, 5s);
	z-index: 2;
}

vendorMixin.scss

@mixin vendor($property, $value){
	-webkit-#{$property}	:$value;
	-moz-#{$property}	:$value;
	-ms-#{$property}	:$value;
	-o-#{$property}		:$value;
	#{$property}		:$value;
}