Java. The bane of most IT professional’s existence. Most websites don’t use the plugin, instead opting for modern Web standards. Java is renowned for being riddled with bugs and security issues. Homeland Security has previously warned users about using the software. Simply disable and uninstall it if you know you don’t need it.
Meanwhile, apps like Adobe Flash and Adobe Reader are also known to be troublesome, but are still widely used. Your best bet is to make them update automatically in the background. There’s advice on how to do this for both Flash and Reader.