This should be integrated into the XBL/Wii codes thread, but whatever. I couldn't find a thread like this, so, I give to you, the Nintendo DS Friend Code thread.

My codes:
Metroid Prime Hunters - 1160 9573 9489
Mario Kart DS - 021606 454580
Advance Wars: Days of Ruin - 051672 126216
Legend of Zelda: Phantom Hourglass - 4640 0992 1188
Tony Hawk's American Sk8land - 219175 031026

I'm up for challenges.