You can also have some fun with aliases and make users go crazy; take a look at this alias:
elliot@ubuntu-linux:~$ alias nano="vi"
Now when user elliot tries to open the nano editor, the vi editor will open instead! User elliot can overcome this dilemma by typing in the full path of the nano editor. Here is another funny alias:
elliot@ubuntu-linux:~$ alias exit="echo No I am not exiting ..."
Now look what will happen when user elliot tries to exit the Terminal:
elliot@ubuntu-linux:~$ exit
No I am not exiting ...
elliot@ubuntu-linux:~$ exit
No I am not exiting ...
I will let you deal with this by yourself; I am evil like that! Haha.