I find Gemini Deep Think to be unbelievably underrated. In my testing, it consistently comes out far ahead of any other model or harness (for system architecture debugging, coming up with excellent YouTube title and hook ideas, etc). You can through a ton of context at it, and Deep Think's attention to detail is excellent.

My only exceptions being Sonnet 4.5 / Codex for code implementation, and Deep Research for anything requiring a ton of web searches.