Kid Icarus is up as a 3D Classic, so if you didn't play it on the NES now is a good time to try it out. The semi-sequel, Of Myths and Monsters, is also on the VC, and it is pretty fun too.
My favorite game of all-time, Punch-Out!!! is also up for download. If you never played it, give it a try: It's equal parts amazing and difficult. I still play my regular NES copy on a semi-weekly basis to keep my skills up. Disclaimer: The VC version is Punch-Out!!! featuring Mr. Dream, not Mike Tyson's Punch-Out!!!. The games are identical (Mr. Dream is a re-skinned Iron Mike), but I'll always love the version I played first, with Mike Tyson, over the retooled version.
Ninja Gaiden is great and cheap. If you are a purist, go ahead and download: It is the NES version, NOT the "meh" arcade version or the SNES "Greatest Hits" version with the sucky soundtrack.
Shantae, a DSi title, is absolutely excellent as well. Save a few bucks on that $50 for when the GBC original is put up on the VC.
Finally, since you can't really find physical copies of Fire Emblem: Awakening too easily (yet), consider giving it a download. Aside from Kid Icarus: Uprising, it is the best 3DS game yet.
I hear Unchained Blades is pretty good, but I've never played it. Nor do I know what it is even about. But if others are to be believed, it is worth the money. I'll be downloading it after I finish Fire Emblem (i.e. probably never).
Hope that helps a bit.
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