Make any 2D shooter you want, as long as it's significantly more complex than Taito's Space Invaders. One category allows NES entries. See Official Rules for details.
However, there seems to be a practical conflict in the rules:
This seems to claim that entries that don't run on hardware are in danger of disqualification. In addition, at least one user of message boards on this site has threatened physical violence on anybody who publicly distributes an iNES binary that hasn't been tested on a rewritable NES cartridge. Under normal circumstances, the majority that does not own a rewritable NES cartridge would be able to send a copy to a forum member to test, but the rules also state the following:Beside GP32 and DC all other entries will be tested using emulators or if a judge has hardware avaliabe on the real system.
I wonder what "spread" means in this context. Would giving NDA'd access to the binary to another nesdev member constitute "spreading"? If not, then which members are willing to test MMC3 code on an NTSC Famicom or NES?Do NOT spread your submission before the official results are announced, posting screenshots is okay, but not the binary.
Or should I stick to a category 2 (GBA) entry, given that I own two different brands of rewritable GBA cart?