Microsoft Remote Desktop: Microsoft's native client for Remote Desktop Protocol. It's available on multiple platforms including Windows, macOS, iOS, and Android.
rdesktop: This is an open-source client for Windows Remote Desktop Services, capable of natively speaking Remote Desktop Protocol (RDP) in order to present the user's Windows desktop.
Chrome Remote Desktop: This is a Google Chrome browser extension that allows you to remotely access another computer through Chrome browser or a Chromebook.
FreeRDP: A free remote desktop protocol library and clients. This open-source solution provides a highly compatible RDP client that can connect to a wide range of RDP servers.
Remote Utilities: This is a RDP solution for Windows that provides highly configurable access permissions, allowing you to set up your connection as per your needs.
AnyDesk: It's not strictly an RDP client (as it uses its own proprietary protocol), but it's commonly used for the same purpose as RDP clients - remote desktop control.
Remember that the effectiveness of these tools can depend on your specific needs and the configuration of both the client and server machines.