Even though the DS a very popular, new platform, there are now a number of great games that you can find at an impulse-buy price level. Since the DS is so popular, there aren’t a lot of good titles under $10, so I’ll set our mark at $15. Yes, I know, the DS isn’t retro at all, but most of these games are either old-school or retro in nature and should be enjoyed by even the most hardcore of classic gamers. (Prices listed are an average eBay price for US games, including shipping.)