Mullvad VPN is one I use as needed. You can sign-up for as little as a month, and doesn't require any type of personal info to setup. Not even an email address. You can pay by multiple means which then gives you a downloadable receipt with a code. Apply the code in your installed VPN apps activates the service. You can use the same code on multiple devices.
Mullvad servers are available around the world, 15 in the U.S. alone, and I found it to be among the fastest VPNs. I use this service primarily if connected to public/unencrypted/unknown WiFi while traveling.
I've also found it useful when using my wireless internet service, as it typically indicates my IP in a different state. Using Mullvad from a local location solves the issue of not having access to online film festival screenings in my area. Even-though I'm technically accessing the screenings locally, my out of state internet IP address will otherwise block access as being not licensed in that area.