(You can pick up to three)
See post below for details:
This post is a wiki - please feel free to add/edit as needed (please follow the same format/alphabetical order).
AbsoluteTelnet / SSH is a telnet and SSH client for Windows! A secure flexible SSH client with SFTP file transfer and rock-solid emulations that is suitable for developers, administrators, or deployment across the enterprise. It includes the industry standard SSH protocols to secure terminal session data across insecure environments such as the internet. Its new tabbed interface is a favorite among AbsoluteTelnet users, and new features are being added all the time! If you need unrelenting performance and unmatched features, then AbsoluteTelnet is what you’ve been looking for. Download it now and take it for a spin!!
Alacritty is a modern terminal emulator that comes with sensible defaults, but allows for extensive configuration. By integrating with other applications, rather than reimplementing their functionality, it manages to provide a flexible set of features with high performance. The supported platforms currently consist of BSD, Linux, macOS and Windows.
The software is considered to be at a beta level of readiness; there are a few missing features and bugs to be fixed, but it is already used by many as a daily driver.
OmniCom Technologies, Inc. offers a robust multi-session terminal emulation through AlphaCom terminal emulation, for Windows 10/8.x/7/Vista/XP/200x/NT/ME/98SE and OSX 10.9 or higher with support for SSH, Telnet, LPD, high volume printing, file transfer, dynamic font sizing, auto-login, and much more. Try before you buy. Our AlphaCom software is free to download and use for 30 days, hassle-free.
ConEmu-Maximus5 aims to be handy, comprehensive, fast and reliable terminal window where you may host any console application developed either for WinAPI (cmd, powershell, far) or Unix PTY (cygwin, msys, wsl bash).
As Windows console window enhancement (local terminal emulator), ConEmu presents multiple consoles and simple GUI applications (like PuTTY for example) as one customizable tabbed GUI window with various features.
Moreover, due to deep integration, ConEmu is the best companion for Far Manager (FAR in Wikipedia), my favorite shell replacement.
Terminal is a terminal emulator application for accessing a UNIX shell environment which can be used to run programs available on your system.
Terminal supports escape sequences that control cursor position and colors.
Multiple GNOME terminals in one window!
Terminator was originally developed by Chris Jones in 2007 as a simple, 300-ish line python script. Since then, it has become The Robot Future of Terminals. Originally inspired by projects like quadkonsole and gnome-multi-term and more recently by projects like Iterm2, and Tilix, It lets you combine and recombine terminals to suit the style you like. If you live at the command-line, or are logged into 10 different remote machines at once, you should definitely try out Terminator.
Screen is a full-screen window manager that multiplexes a physical terminal between several processes, typically interactive shells. Each virtual terminal provides the functions of the DEC VT100 terminal and, in addition, several control functions from the ANSI X3.64 (ISO 6429) and ISO 2022 standards (e.g., insert/delete line and support for multiple character sets). There is a scrollback history buffer for each virtual terminal and a copy-and-paste mechanism that allows the user to move text regions between windows. When screen is called, it creates a single window with a shell in it (or the specified command) and then gets out of your way so that you can use the program as you normally would. Then, at any time, you can create new (full-screen) windows with other programs in them (including more shells), kill the current window, view a list of the active windows, turn output logging on and off, copy text between windows, view the scrollback history, switch between windows, etc. All windows run their programs completely independent of each other. Programs continue to run when their window is currently not visible and even when the whole screen session is detached from the users terminal.
Guake is a python based dropdown terminal made for the GNOME desktop environment. Guake’s style of window is based on an FPS game, and one of its goals is to be easy to reach.
iTerm2 is a replacement for Terminal and the successor to iTerm. It works on Macs with macOS 10.14 or newer. iTerm2 brings the terminal into the modern age with features you never knew you always wanted.
Konsole is also integrated into multiple other KDE Applications making it easier to reach and more convenient. For example, KDevelop, Kate and Dolphin all use Konsole as an integrated terminal emulator.
- Xterm-compatible terminal emulation, coverage of all DEC terminal series screen control features.
- 256 colours and True-Colour support, optional CMYK colour specification.
- Full Unicode support, comprehensive character encoding support and wide character handling.
- Bidirectional rendering, flexible bidi controls.
- Full character attributes support, including italic, underline styles and colours, overline, strikeout, rapid blinking.
- Extended character attributes support: shadowed, subscript, superscript (terminfo) and overstrike.
- Alternative fonts: simultaneous display of multiple fonts.
- Secondary fonts: script-specific alternative font usage.
- Reflow option on terminal resize (re-breaking of wrapped lines).
- Image display support.
- Sixel graphics support.
- Full emoji support, including all emoji sequences.
- Tektronix 4014 vector graphics emulation.
The mrxvt program is a terminal emulator for X Window System. It provides DEC VT102 compatible terminals for programs that cannot use the window system directly.
PuTTY is an SSH and telnet client, developed originally by Simon Tatham for the Windows platform. PuTTY is open source software that is available with source code and is developed and supported by a group of volunteers.
SecureCRT client for Windows, macOS, and Linux provides rock-solid terminal emulation for computing professionals, raising productivity with advanced session management and a host of ways to save time and streamline repetitive tasks. SecureCRT provides secure remote access, file transfer, and data tunneling for everyone in your organization.
TeraTerm Project would have been developed terminal emulator “Tera Term” and SSH module “TTSSH”. This software is open source software under BSD License. This is Tera Term Pro 2.3 succession version and is being officially recognized by the original author. Development is continuing in Project Page on GitHub.
Built in terminal emulator for macOS
Terminator is an open-source terminal emulator implemented in Java. The original implementation and documentation was written by Phil Norman. The original idea of having a suitably hackable terminal emulator with which to experiment with advanced features came from Elliott Hughes, and he turned Phil’s component into an application.
Termux is an Android terminal emulator and Linux environment app that works directly with no rooting or setup required. A minimal base system is installed automatically - additional packages are available using the APT package manager.
Become a command line power user on day one. Warp combines AI and your dev team’s knowledge in one fast, intuitive terminal.
Windows Terminal is a multi-tabbed terminal emulator developed by Microsoft for Windows 10 and later as a replacement for Windows Console.
The xterm program is a terminal emulator for the X Window System. It was originally developed in the mid-1980s to provide DEC VT102 and Tektronix 4014 compatible terminals for programs that cannot use the window system directly.
Yakuake is a drop-down terminal emulator based on KDE Konsole technology.
Features:
Smoothly rolls down from the top of your screen
Tabbed interface
Configurable dimensions and animation speed
Skinnable
Sophisticated D-Bus interface
ZOC Terminal is a professional terminal emulation software for macOS and Windows.
Its impressive list of emulations and powerful features make it a reliable and elegant tool for connecting to hosts and mainframes via Secure Shell, Telnet, serial cable and other communication methods.
With its modern user interface, this terminal has many features that will make your life easier. In its own way, ZOC is the Swiss army knife of terminal emulators: Versatile, robust, proven.
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. It’s still a useful utility for those systems that only offer dialup connections and for connecting to devices through a serial port, like many routers. For newer Macintoshs that don’t have a normal serial port, ZTerm can talk to ports on USB to serial adapters, through the appropriate driver software supplied with the adapter.
It’s foot on Linux (Wayland) over here. Downside is that it’s unknown to cf, which is used by Rebar3 for deciding whether to support colored output 
(Non-issue if you use tmux/screen/whatever anyway.)
Oh and Termius on Android.
cool-retro-term when I feel nostalgic 
Recently decided to switch from iTerm2 to WezTerm - Wez's Terminal Emulator
Emacs.