I'm gifting my friend's child a handheld emulator and loading it up with games. It's capable of playing things pretty much up to Nintendo GameCube (It's even running Twilight Princess, though it studders in some areas).
I've got pretty much everything that exists for NES, SNES, N64, as well as a couple dozen games for Genesis. I never had a Sega Saturn or a PS / PS2 growing up though and I'm wondering what I should grab for those, as well as some more obscure GameCube titles if there are any I should know about.
Here's your chance to wax nostalgic about some old games and help ensure they make it into a kid's present. Even if I have the game already, I can still throw suggestions into the "favorites" list and make them easier to find.
If PS2 is runnable:
PSP
GCN
Dreamcast
Also a recommendation that you don't have to take- don't dump entire romsets onto the kid because it might overwhelm him. If you do decide to do this at least give him a list of games you think he should try on that console or point him towards something online that tells him the best games on each console so he isn't just lost.