CUSTOM PREVIEW - you can change this in the previewTemplate option

.toolbar-icon-admin-toolbar-tools-help:

.toolbar-icon-edit:

.toolbar-icon-entity-user-collection:

.toolbar-icon-escape-admin:

.toolbar-icon-help-main:

.toolbar-icon-help:

.toolbar-icon-home:

.toolbar-icon-link-toolbar-menu:

.toolbar-icon-menu:

.toolbar-icon-shortcut:

.toolbar-icon-system-admin-config:

.toolbar-icon-system-admin-content:

.toolbar-icon-system-admin-reports:

.toolbar-icon-system-admin-structure:

.toolbar-icon-system-modules-list:

.toolbar-icon-system-themes-page:

.toolbar-icon-toolbar-menu:

.toolbar-icon-user:

Embedded SVG option

(The data-grunticon-embed attribute tells grunticon to inject SVG inline):

icon-burger:

icon-burger (styled variation):