Simple Chrome extension that lets you select emails and encrypt or decrypt them. Public keys aren't negotiated automatically intentionally and should be managed manually and externally (for fun).

App that lets you take a photo of a scenery or landmark and suggests poses of other people.

Simple app to keep track of interactions you've had with people and store events or plans you made with them. Could have some friend group mechanic where you can keep track of how people are connected.

Software that handles all formatting so scanlation gets easier and people don't have to manually clear boxes etc.

Feed your manuscript to a local model and ask questions about it. Mostly for fun. Could make characters actually converse with each other etc.

Aggregate real estate listings in the area, the closest bus/train/metro stops, daily commutes etc and show comparisons.

Rubber duck avatar that sits at the bottom right of desktop and nods and emotes when you talk, but doesn't actually do anything else.

Some people don't like onboarding new people or processes might be unclear. Create a customizable tamagotchi-like pet that is a virtual representation of a new hire to encourage training.

Simple to-do list, but every task is turned into a simple boss battle-esque animation. Completing tasks means you defeat them.