Bigger Glyphicons

Here's how I do it:

<span style="font-size:1.5em;" class="glyphicon glyphicon-th-list"></span>

This allows you to change size on the fly. Works best for ad hoc requirements to change the size, rather than changing the css and having it apply to all.

You can just give the glyphicon a font-size to your liking:

span.glyphicon-link {
    font-size: 1.2em;
}

The .btn-lg class has the following CSS in Bootstrap 3 (link):

.btn-lg {
  padding: 10px 16px;
  font-size: 18px;
  line-height: 1.33;
  border-radius: 6px;
}

If you apply the same font-size and line-height to your span (either .glyphicon-link or a newly created .glyphicons-lg if you're going to use this effect in more than one instance), you'll get a Glyphicon the same size as the large button.

<button class="btn btn-default glyphicon glyphicon-plus fa-2x" type="button">
</button>

<!--fa-2x , fa-3x , fa-4x ... -->
<button class="btn btn-default glyphicon glyphicon-plus fa-3x" type="button">
</button>