Fish shell is a modern command shell that offers great features. One of my favorite is that fish will parse man pages and provide command hints as you type a command. More about fish shell can be found at http://fishshell.com/.
Fish shell can be easily install on Ubuntu with the following commands.
sudo apt-add-repository ppa:fish-shell/release-2 sudo apt-get update sudo apt-get install fish
This command makes fish the default shell.
chsh -s /usr/bin/fish