Defender of Oasis is probably one of the best RPG's for this system. If for no other reason, here is why it is the best:

1) you can turn it off at any time, auto-save. Who ever came up with the idea that you have to get to the dungeon exit or save point to save the game? Do these people have eternal batteries and no other obligations? 'DOO' allows you to stop at any time and start exactly where you stopped.

2) No freakin passwords or codes, you save to the cartridges built-in memory on this title.

In addition to that, great sound and grafics on this title.
It's an extremely rare title, if you find it get it.

The game itself doesn't give you tremendous leeway on what you can do but nonetheless it is a great game that can last you throughout a whole trip. I have played this title over 5 times and still enjoy it. All RPG's (especially portables) should have that save feature!