I don't have time or resources to make these, so here you go for the next hackathon:
1. Decentralized video communication platform. Basically live video/audio chat with Theta bandwidth sharing. Discord, Teams and the like all rely on centralized servers, so this would be a real useful thing.
2. A receipt token for staked theta and a smart contract to handle it. That way you can use staked theta as collateral, or even payment while still gaining TFUEL rewards from staking. The TFUEL rewards would be gotten when handing in the receipt-token.
3. A bandwidth booster browser plugin for arbitrary video content via a tracker. Suppose I am watching or have watched a video on youtube, I can tell my plugin to cache it in various qualities which then tells the tracker that that video is available for boosting. When someone else then goes to watch that video, or searches the tracker for it, I will contribute by sending cached parts of the video when they watch it on youtube, seamlessly. Seems far out, but should be possible. Like bittorrent built into the browser. The most complex dapp, but would drive the most adoption. The tracker also tells you what content is being boosted so you can seek out boosted content and actively use the theta network.