Recently a team of developers from "omnimaga" have ported a modified version of the classic fps shooter "Doom" to the TI-Nspire and have plans to release a fully functioning version to the public soon.
The actual version is called nDoom, which is a modified edition of the original that is designed to work on less powerful machines. While you may not expect such a device to have enough graphical power to truly pull this off, this whole thing is definitely a case of "you've got to see it to believe it."
Oh and I nearly forgot, the calculator can now connect to the INTERNET! Well a type of internet, at least, called Global CALCnet 2.2. While 'local' CALCnet 2.2 allows between two to two million calculators to connect in local-area networks, Global CALCnet can link multiple CALCnet networks across the internet, and can even offer internet-based services to calculators, such as connections to Internet Relay Chat and other chat protocols, and even multi-player games such as Scorched-Earth are currently in the works.
Sure it may cost around $100 but wouldn't it be worth it to get a calculator that allows you to play games in class...