Sass mixin for arrows based on The Shapes of CSS from Chris Coyier http://css-tricks.com/examples/ShapesOfCSS/

arrows.scss

// --------------------------------------------------------
// arrows
// --------------------------------------------------------
// $direction: top, left, right, bottom, top-left, top-right, bottom-left, bottom-right
// $color: hex, rgb or rbga
// $size: px or em
// @example
// .element{
//     @include arrow(top, #000, 50px);   
// }
@mixin arrow($direction, $color, $size){
    display: block;
    height: 0;
    width: 0;
    
    @if $direction == 'top' {
        border-left: $size solid transparent;
    	border-right: $size solid transparent;
    	border-bottom: $size solid $color;
    } @else if $direction == 'right' {
        border-top: $size solid transparent;
        border-bottom: $size solid transparent;
    	border-left: $size solid $color;
    } @else if $direction == 'bottom' {
        border-top: $size solid $color;
        border-right: $size solid transparent;
        border-left: $size solid transparent;
    } @else if $direction == 'left' {
        border-top: $size solid transparent;
    	border-right: $size solid $color;
    	border-bottom: $size solid transparent;
    } @else if $direction == 'top-left' {
        border-top: $size solid $color; 
        border-right: $size solid transparent;	
    } @else if $direction == 'top-right' {
        border-top: $size solid $color; 
        border-left: $size solid transparent;
    } @else if $direction == 'bottom-left' {
        border-bottom: $size solid $color; 
        border-right: $size solid transparent;	
    } @else if $direction == 'bottom-right' {
        border-bottom: $size solid $color; 
        border-left: $size solid transparent;
    }
}