You can open any of the standard GUI applications (such as Mail, Explorer, Address Book, etc.) from a terminal session. Although this may not have great benefits in day to day use (why not just click the dock icon?), it does imply that you could write a shell script to open a GUI app, and then use the UNIX cron program to schedule the 'open' to happen on a shedule. If the GUI app you open then had some command it executed at startup, this might prove to be a worthwhile trick.
In any event, to open a command in the terminal, just type
open /path/to/application/bundle
For example, to launch the Calculator or the game, type one of the following:
open /Applications/Calculator.app/
open /Applications/GrabBag/chess.app
As I said, I'm not completely certain about why or how useful this is, but it is somewhat interesting. It even opens the application in the background, so you don't switch out of your terminal window.