"Do I Need a Gaming Mouse?"

Ultimately, no. 

However, "Would a Gaming Mouse Make My Gaming Experience More Enjoyable?"

Most likely.

Below is a rather tongue in cheek attempt at a list of advantages of a gaming mouse over that of a regular mouse, where certain aspects may appeal to you and some won't. It is also worth bearing in mind that different models of both a gaming and non-gaming mouse will have their very own unique strengths and weaknesses and hence may not apply.

Why Get a Gaming Mouse?

They offer additional ergonomic buttons and configurations that are programmable to be customizable to your very own preferences, allowing it to be custom built for your gaming style as well as saving you from having to refer to the keyboard. Just to give you an example the Logitech Wireless Gaming Mouse G700 offers you an additional '13 programmable buttons' to that of an ordinary mouse -- helping you save just those extra few milliseconds (and effort) that would have probably been spent bent over a keyboard -- which in the gaming world could literally mean the difference between life and death.

Built for your hand, Sleek and All Good Looking -- often compared to that of a standard mouse, the gaming mouse looks like a whole new breed, they are specifically modelled and sculpted to match your hand shape resulting in faster game play and are made sleek enough to make the gaming as comfortable as possible (often with the inclusion of anti-slip rubber coating). Plus the fact that most of them just look... really, really good.

Almost frictionless -- especially with the more expensive models such as the Logitech Wireless Gaming Mouse G700 you should notice an incredible difference in the movement and glide over the mouse mat compared to the rigidness of a common mouse. Giving you the advantage to quickly and effortlessly maneuver the mouse without concern for the adjustment of friction.

Improved cursor control -- with many of the gaming mice, they are especially designed to offer complete cursor control with the inclusion of advanced 'high precision gaming lasers' to offer the precise whereabouts of the movement of the cursor despite your rapid hand movements. Many of the more advanced gaming mice offer you both the advantages and disadvantages of the wired and wirless gaming mouse, so you can choose which makes you feel more comfortable when playing.

Ultimately they give you an advantage over other gamers, they allow you to be faster, more accurate, more control, and more comfortable -- hence you are likely to perform better 'in game' than if you had to use a regular mouse.

So although the gaming mouse is not essentially needed, you can see from above that with certain models they have the potential to offer you a whole new dimension to PC and online gaming. Let me know if the above features influenced your original answer to the question in any form, 'Do I need a gaming mouse?', below.