Ones I use a lot are:-
Simply to exit terminal quickly
To quickly view the grub menu of my five OS machine
To view all recently installed packages
alias menu='grep "menuentry " /boot/grub/grub.cfg | cut -c 1-100'
To view all recently removed packages
alias install='grep -iw install /var/log/dpkg.log.1 && grep -iw install /var/log/dpkg.log'
To see all recently upgraded packages.
alias remove='grep -iw remove /var/log/dpkg.log.1 && grep -iw remove /var/log/dpkg.log'
I also have openssh-server installed but to stop it opening on bootup as I need it only occasionally, I comment out the line
alias upgrade='grep -iw upgrade /var/log/dpkg.log.1 && grep -iw upgrade /var/log/dpkg.log'
in /etc/init/ssh.conf which stops the server before it even starts. I then use aliases
# start on filesystem
to start and stop ssh server when I need to, just for my system's added security..
alias ssh+='sudo service ssh start'
alias ssh-='sudo service ssh stop'