Remmina - Remmina is a remote desktop client written in GTK+, aiming to be useful for system administrators and travellers, who need to work with lots of remote computers in front of either large monitors or tiny netbooks.
TeamViewer - TeamViewer lets you establish a connection to any PC or server within just a few seconds.
Xpra - multi-platform screen and application forwarding system
mRemoteNG - mRemoteNG is a fork of mRemote, an open source, tabbed, multi-protocol, remote connections manager.
X2Go - Get X2Go. Installing X2Go (client/server). Download X2Go Client (Windows installer (XP and Later), OS X 10. 9 and higher DMG, OS X 10. 10 and higher DMG or macOS 10.
join.me - Instant screen sharing. Instant Aha!