A designers most used function:

In SCSS I use a very simple mixin for rounded corners, something I use frequently when designing sites.

  @mixin radius($dist) {
    border-radius:$dist;
    -moz-border-radius:$dist;
    -webkit-border-radius:$dist;
    -khtml-border-radius:$dist;
    -webkit-background-clip:padding-box;
  }

Then in the class just add:

  @include radius(5px);