Pictochat is a great way to talk to friends when you don't want your conversation to be heard by others.

User Rating: 9.2 | PictoChat DS
I enjoy using pictochat with my friends on the bus when we don't want our conversation to be heard but we want to talk to each other. There are 4 chatrooms you can enter, and each chatroom supports 16 DSs at the same time. Talk about a massive conversation with friends! The great thing is that the pictochat is a free part of the DS when you buy it, so there is no need to spend $20 or $30 on a game. You can do this by yourself, but if you have friends in the same chatroom, this is probably one of the funniest things the DS has to offer. Sometimes, people with DSs that you don't even know will go into your chatroom, and it is awesome to make a new friend. Everybody has to be within roughly 30 feet of each other person is the only downside if you have like more than 10 or 12 people in a chatroom. Overall, this is the best free thing, along with DS Download play, that is offered on the NIntendo DS