Media Card readers are for all intents and purposes, obsolete. MOST media card using devices can be plugged in via usb cable anyways and will function as their own reader.
If you haven't needed on before, I wouldn't bother buying one. That being said, internal units are far superior to external units, but more time consuming for initial set up. For what it's worth, most laptops have an SD slot, and most micro/mini SD's can be adapted to fit said slot.
I don't know of any game using SD, however it is a nice tidy little format if you don't like USB key's for transferring files/backing up save files.