I just added app-shells/fish to the tree. It’s a shell with syntax highlighting, awesome tab completion, and more. The tab completion for man pages, for example, actually includes the description of the command from whatis.
Look at the screenshots.
Update: More cool stuff about fish: It has really good error reporting, so it’s easy to find problems. If you type ‘help’ in the shell, it opens a browser (an X-based browser if DISPLAY is set, otherwise something like links/lynx) — This is cool because you get hyperlinks. Reworked syntax for much of the shell scripting features is self-consistent and easy to understand.