Counter-Strike: Global Offensive is an online first-person shooter game developed by Valve Corporation and Hidden Path Entertainment and released on Steam, Xbox 360, and PlayStation 3.

Enhancements

Playing at 4:3 1440x1080 stretched resolution

Playing at a resolution of 1440x1080 gives the advantage of being high definition while also increasing the size of player models ingame, thereby making it easier to spot enemies.

nVidia users:

Open nVidia control panel
Click on Display -> Change Resolution
Click Customize
Click on Create Custom Resolution
Set the Horizontal pixels to 1440
Set the Vertical lines to 1080
Click Test
When the dialog asking you if you want to save the resolution or not pops up, click Yes
Click OK
Open Steam and right click on CS:GO in your Steam library
Click Properties -> Set Launch Options
Copy and paste -full -w 1440 -h 1080
Click OK
Play CS:GO

If you're having issues with CS:GO displaying at a non-stretched resolution with black bars then follow these steps:

Fixing non-stretched resolution in CS:GO:

Open nVidia control panel
Click on Display -> Adjust desktop size and position
Under scaling, select Full-screen
Click apply
Run CS:GO