On a client running Windows 8 (using Remote Desktop Protocol 8.0) you’re now able to dynamically turn on and off the RDP setting Smart Sizing.
This allows you to resize the RDP screen to scale it to your needs. Before RDP 8.0 you had to change this settings in the .RDP file before connecting. You can now dynamically switch this on and off while running the session without having to disconnect and reconnect.
Credits to fellow MVP Shannon Fritz for pointing this out: