fire emblem except it's a competitive TCG and stored on atproto
battle network type thing where viruses get generated and pointed at random records and interacting with those records can initiate a net battle please pick this one I think it would be the coolest thing in the world also it has good synergy with the one below this
Monster Rancher using Atproto to generate monsters like they used other game discs on the ps2
cohost on atproto would be funny
timeknife - a Constellation-like microservice that implements a lexicon-agnostic and tunable form of the bluesky lossy timeline system described in Jaz's blog post.
poker on atproto as a proof of concept of modeling turn based multiplayer games with nondeterminism and hidden information using hashes followed by reveal actions combined with seeded CPRNGs. Go Fish would also work and probably be at least a little simpler.