Formal:
* Pioneering: This emphasizes the groundbreaking nature of the thing.
* Innovative: This highlights the new and original aspect.
* Seminal: This suggests that the thing is foundational and influential.
* Inaugural: This implies the beginning of a new era or trend.
* Unprecedented: This means something has never happened before.
* Groundbreaking: This suggests the thing is revolutionary and changes the landscape.
Informal:
* First-ever: This is simple and straightforward.
* Original: This focuses on the uniqueness of the thing.
* Novel: This implies the thing is new and interesting.
* Trailblazing: This emphasizes the leadership role of the thing.
* Revolutionary: This implies the thing is radical and transformative.
The best word to use will depend on the specific context and what you want to emphasize.