Bareback It

Estimated Cost: $0

Anti-virus and firewall programs are really important for when you're browsing the Internet for obscure pornography, but there really aren't too many opportunities for viruses to be transmitted over standard game infrastructures.

Unless you're downloading player made maps and mods, you're not likely to transmit any PC debilitating software, which means that the extra memory and bandwidth taken up by your anti-virus software can be made free and clear by deactivating it during gameplay.

It may seem like a crazy move if you're deathly afraid of spyware, but it's a risk worth taking if you care about performance.