I like the "antennas" feature a lot

For the uninitiated, Firefish's antennae are saved searches, where you can specify lists of keywords and users and come back to them over and over again. It's similar to Mastodon's hashtag follow feature, only more flexible. Though, IIRC, it doesn't add the search results to your home feed; it keeps them separate, and undiluted.

From an administrator's point of view, Firefish's Recommended timeline is super cool, and is similar to Akkoma's 'bubble' feature. It lets you specify a list of other federated servers to display posts from, creating a kind of "super-local" timeline. It's the kind of thing I'd love to see in Lemmy and kbin.