Minimizing Web Browser Attack Surface
gfx.downloadable_fonts.enabled media.autoplay.enabled (autoplay of <video> and <audio> tags) media.*.enabled (enables/disables individual codecs etc.) network.http.spdy.enabled
Disabling downloadable fonts will break the icons on some web sites, but on the other hand I thinks it’s a well worth security enhancement since font loading and rendering is quite complex and must be bug-prone.