For years I've been carrying around all my DS games, along with my GBA games, in a very old GameBoy Advance carry case, designed for carrying the GBA with just a few of those games. It has been quite inconvenient for a while as it took up a lot of space, plus I realised I didnt need to carry around my GBA games anymore really, as I rarely played them, so decided it was time to get something to carry my 20ish (at the time) DS game cartridges.
This one was ideal. It's compact and can easily carry 24 game cartridges securely and protect them from most harm. It's easy for taking games on holiday or even just carrying them around in a handbag or something, and will protect them if dropped or something as the plastic case is quite sturdy. I doubt it would survive from any strenuous breakages or really high drops (then again, most stuff wouldn't), and I am unsure if it would prevent water from seeping it, so those are things that you might need to take into account. However, I use mine to store my DS game cartridges and take them with me when necessary, and as long as you are sensible about what you do with it it will protect your game cartridges and make it easier to transport them. Lightweight and sturdy.