Instead of trashing that obnoxiously loud mouse to get a new one, save some money and the environment by modding it into a Ninja Mouse. All you need in a thin knife and whichever type of screwdriver to open it.
NOTE: This mod can takes only a few minutes if you know what to look for. I think it goes without saying, but mod at your own risk.
Step 1: First, Some Numbers
Using an Android decibel meter, I got the following data:
-Ambient Noise 48 dB
-Ninja Mouse 52 dB
-Regular Mouse 74 dB
(The regular mouse is just as loud as my Ninja Mouse used to be.)
If you know about logarithmic scales, you can see Ninja mouse is over 10 times quieter than the regular mouse!
Step 2: Open It Up
There are a lot of different types of mice out there and most all employ means of hiding their screws. Check under the plastic pads and in the battery compartments if you're having trouble finding them.
When you get inside, locate the mouse switches. You should see some rectangular boxes like in picture 3. If you have the square switches like in picture 4, you're out of luck. There isn't a way to quiet them down that I found. (They use a thin, metal concave disk than flips to being convex when pressed. Putting anything in there to quiet it down makes it lose all functionality.)
Step 3: Open Up the Switches
Open up the switch by inserting the tip of your knife into the clip of the switch cover and gently twisting the knife until it unlatches. Unlatch the other side, it should be easier.
Do this in an area where with dark flooring. That little white button likes to get away and it's really hard to find on a white floor.
Step 4: Press Down the Tab
Using your knife again, push the tab down to shorten the gap between the contacts. Test the switch and its loudness by pressing down on the cross member where the white button would normally press.
If you bend the tab down too far, just bend it back with the knife. The metal is quite malleable.
Step 5: Put the Cover Back On
Once you're satisfied with the sound of all your switches, put the covers back on them. You more than likely lost the white buttons, so you'll want to put them back into their covers using the knife to coax it into the slot. The side of the button with the flanges goes on the inner side of the slot.
ProTip: It's much easier to put the mouse on the cover than it is to put the cover on the mouse. (That dastardly white button!)
Step 6: You're Done
Enjoy your new Ninja Mouse! It's so quiet your boss will think you're being unproductive.