Like all high quality software (e.g. Steam), the OSX version of the Junos Pulse VPN client (and quite likely, other versions) has a beautiful feature that will add itself to the autostart list when you boot.
This isn't done in a way one would normally expect; checking the Login Items for Junos Pulse won't give you any results. Since most people don't need another process draining resources, disabling this can be done via:
launchctl unload /Library/LaunchAgents/net.juniper.pulsetray.plist
Side note: Steam is in the Login Items list, so it can be removed from there.