These are my common SCSS mixins and helpers. Requires bourbon (http://bourbon.io)

_helpers.scss

$buttons-list:  '.btn',
                'button',
                'input[type=submit]',
                'input[type=button]';

$unquoted-buttons-list: ();
@each $button-type in $buttons-list {
    $unquoted-buttons-list: append($unquoted-buttons-list, unquote($button-type), comma);
}

$all-buttons: $unquoted-buttons-list;

@mixin font-size($base-font-size) {
    $rem-ratio: $base-font-size / 16px;
    font-size: $base-font-size;
    font-size: #{$rem-ratio}rem;
}

@mixin filter($value) {
    @include prefixer(filter, $value, webkit spec);
}

@mixin appearance($value:none) {
    @include prefixer(appearance, $value, webkit moz ms o spec);
}

@mixin ellipsis($use: true) {
    @if($use) {
        white-space: nowrap;
        overflow: hidden;
        text-overflow: ellipsis;
        -o-text-overflow: ellipsis;
    }
    @else {
        white-space: normal;
        overflow: visible;
        text-overflow: visible;
        -o-text-overflow: visible;
    }
}

// none | text | toggle | element | elements | all | inherit
@mixin user-select($value: none) {
    -webkit-touch-callout: none;
    -webkit-tap-highlight-color: transparent;
    @include prefixer(user-select, $value, webkit moz ms o spec);
}

// Media Query breaks.
//$break-small: 480px;
$break-device: 600px;
$break-smallscreen: 800px;
$break-large: 980px;
$break-xlarge: 1180px;
$break-xxlarge: 1620px;
$break-tv: 1900px;

@mixin respond-to($media) {
    @if $media == device-max {
        @media only screen and (max-width: $break-device) { @content; }
    }
    @else if $media == tablet {
        @media only screen and (min-width: $break-device + 1) { @content; }
    }
    @else if $media == smallscreen {
        @media only screen and (min-width: $break-smallscreen) { @content; }
    }
    @else if $media == desktop {
        @media only screen and (min-width: $break-large) { @content; }
    }
    @else if $media == desktop-large {
        @media only screen and (min-width: $break-xlarge) { @content; }
    }
    @else if $media == widescreen {
        @media only screen and (min-width: $break-xxlarge) { @content; }
    }
    /* iPhone 5 or iPod Touch 5th generation */
    @else if $media == iphone5 {
        @media (device-height: 568px) and (-webkit-min-device-pixel-ratio: 1.5) { @content; }
    }
}