User blog comment:Plexioth- xD/Monster Hunter 3 Ultimate/@comment-4555457-20120201092930/@comment-70.54.115.32-20120201094852

The 3DS supports DLC thanks to an update. However, Monster Hunter 3G was released before the corresponding dev kits were available, so it won't be built to support that. Monster Hunter 4 might. Dynasty Warriors Versus for the 3DS will feature Nintendo costumes, which you probably have to buy to download.

I don't think Tri G supports it, but it's also possible for things to be unlocked through the 3DS' SpotPass feature. Samurai Warriors Chronicles has stages and weapons that are distributed this way, Dead or Alive Dimensions has costumes, etc.

Actually, the Wii supports DLC if it's downloaded onto an SD card. It's even mentioned in an interview for Tatsunoko Vs Capcom by the game's director, so at least some developers at Capcom must know about it.