If you want a desktop app that lets you use ChatGPT models without having to log in separately, ChatTab is a great option. It's a native macOS app that taps into OpenAI's ChatGPT API, letting you use multiple models like GPT3.5, GPT4 and Claude2. It has a distinctive tab-based user interface, customizable keyboard shortcuts, support for Markdown formatting and iCloud sync. ChatTab also is designed to protect privacy with secure API key storage and conversation history stored locally, so it's a good option if you're concerned about privacy.
Another alternative is the AIML API. This service lets you tap into more than 100 AI models through a single interface, which can dramatically accelerate and lower the cost of building your projects with the latest machine learning technology. It offers serverless inference, which means you don't have to worry about setting up and maintaining servers, and a pay-by-the-token pricing model. That can be good for projects that need a reliable and economical way to tap into a broad range of AI models.