Mouse acceleration on Macs has always been a problem when it comes to playing games where precise aiming is important (e.g. in games like Couter-Strike). There are tools like USBOverdrive and Smoothmouse but since Mavericks (I tried it in Yosemite, too) there is a simple terminal command to remove mouse acceleration and enable 1:1 movement.
1. Open Terminal
2. Enter "defaults write .GlobalPreferences com.apple.mouse.scaling -1"
3. Reboot
4. Be much better in competitive games
1. Open Terminal
2. Enter "defaults write .GlobalPreferences com.apple.mouse.scaling -1"
3. Reboot
4. Be much better in competitive games