Gmail got a bunch of few useful features in the last ween including Gmail mobile version 2.0, canned responses and emoticons support for outgoing messages.
If you prefer to spice up your email messages with emoticons, Gmail has released two kinds of emoticons round static emoticons and square animated emoticons. If you are using visual rich-text editor you might have already noticed the emoticon button, click the emoticon to include them.
Another Gmail Labs feature was released that allows you to send canned responses if you are lazy or you are overwhelmed by the no of messages you get for a common question. Go to settings and Labs tab to activate this feature. Once active type a message once and save it using canned responses button, and then you can use the same message to send everyone later. If you combine this feature with Filters feature of gmail you can create auto responders based on filters you set.
I already have so many add-ons for my GMail, I know something like emoticons would slow it down even more. It does still make it awesome though.