If you just want to disply a word or a short text, possilby multi-line, as large and as quickly as possible on your screen, then screen-message is the right tool for you. It has been used already twice at a Debian conference for the Mugshots.
screen-message will display a given multi-line message as large as possible, fullscreen and black on white. You can specify the text either when launching screen-message, or edit it while the program is running.
It is useful to send messages across a room, e.g. during an university lecture. For fast startup, it is recommended to bind it to a key in your desktop environment.