Using a list to dynamically create classes for an icon font

icons.scss

// All of our icons
$icons: (
    (exclaim, "\21"),
    (x, "\78"),
    (play, "\25b7"),
    (user, "\2603"),
    (search, "\2604"),
    (menu, "\2637"),
    (loading, "\2668"),
    (flag, "\2690"),
    (speech, "\1f4ac"),
    (heart, "\2764"),
    (arrow-down, "\2193"),
    (arrow-up, "\2191"),
    (trending, "\2197"),
    (clock, "\29d6"),
    (popular, "\260d"),
    (dollabills, "\24"),
    (thumbs-down, "\1f44e"),
    (thumbs-up, "\1f44d"),
    (circle-right, "\21e8"),
    (circle-left, "\21e6"),
    (circle-down, "\21e9"),
    (circle-up, "\21e7"),
    (globe, "\1f310"),
    (check, "\2713"),
    (mic, "\1f3a4"),
    (carrot-down, "\21a7"),
    (disk, "\1f4be"),
    (eye, "\1f638"),
    (trash, "\74"),
    (paper, "\1f4f0")
);

// Mixin for use inside media queries
@mixin icon($char: false, $defaults: false) {
    @if($defaults == false) {
        font-family: 'icons';
        speak: none;
        font-style: normal;
        font-weight: normal;
        font-variant: normal;
        text-transform: none;
        line-height: 1;
        -webkit-font-smoothing: antialiased;
        -moz-osx-font-smoothing: grayscale;
    }

    @if ($char) {
        content: iconChar($char);
    }
}

// Helper function to get a character code
@function iconChar($key) {
    @each $i in $icons {
        @if nth($i, 1) == $key {
            @return nth($i, 2)
        }
    }

}

// Base Icon transparent class to extend from
%icon {
    @include icon();
}

// Declare transparent classes
@each $i in $icons {
    %icon-#{nth($i, 1)} {
        content: nth($i, 2);
        @extend %icon;
    }
}

usage.scss

.my-thing {
    &:before {
        @extend %icon-exclaim;
    }
}

@media (min-width: 50em) {
    // My thing in a media query cannot extend, so uses the iconChar function
    .my-thing {
        &:before {
            content: iconChar('flag');

            // This can also be written this way if the content doesn't
            // already have the base icon styles
            // @include icon('flag')
        }
    }
}