PuTTY is a free and open-source terminal emulator, serial console and network file transfer application.
RealTerm is a terminal program specially designed for capturing, controlling and debugging binary and other difficult data streams.
ZTerm is a terminal emulation program for the Macintosh. In its day, many people used it to connect to Bulletin Board Systems and download files. Now we have the internet.
SSH / Telnet / UART dongles (USB and Bluetooth) / own PTY client for Android.
moserial is a clean, friendly gtk-based serial terminal for the GNOME desktop. It is primarily intended for technical users and hardware hackers who need to communicate with embedded systems, test equipment, and serial consoles.