I'm going to buy a Nintendo DS now. I have given in to the dark side.
Welcome my son. Mohahahaha
Games I recommend:
1. New Super Mario (easy to beat, but you can spend hours and hours finding all the stars/secrets)
2. Mario 64 DS (Even if you are like me and own the original for the N64,this is still worth the $20).
3. Mario Cart DS (So that we can play against each other before CAOS events.)
I recommend the first two as well. They are great games... I don't like Mario Kart as much, but it's still fun. If we verse each other in it, prepare to be owned by my complete lack of power boost skill, hehehe.
Starfox Command is also good... avoid Metroid Prime Hunters. Also, avoid Castlevania: Dawn of Sorrow unless you really feel like being bored for a few hours.
I picked up Advance Wars: Dual Strike for it. I played the one for GBA and really liked it and so far I'm extremely addicted. I plan on buying some Super Mario game whether it be the 64 DS or the New SMB. I think Justin Camerer has Mario Kart DS so we can just play it off of his cartridge.
What I really cannot wait for is the Opera Web browser for the DS (http://www.opera.com/products/devices/nintendo/). I suspect that this may even allow you to use the school's wireless network, because they just use a web-form for authentication. Even if it dosn't work at school, I will still like being able to surf the web from such a cool little device that I already own.
tetris ds is where it's at. you can play 10 person matches, and you only need one cart. also, you can play against up to four people over the internet. fun stuff.