This one slipped past me when it was originally released, but @shmups recently alerted me to the existence of Omidos Entertainment's Clean'Em Up, a neon-colored twin-stick shooter for Windows. A free demo version is also available.

Clean'Em Up puts players in control of an Upgradable Antivirus charged with protecting a PC's file system from viruses and other threats. The game's Back2Back Engine allows you to launch attacks from both the front and the rear of your ship, and there are numerous weapons and power-ups you can collect throughout the 70 included levels.

Clean'Em Up is priced at $3.99.