I used to play a lot of games on miniclip wayyyy back when flash was a thing, but nitrome games were my favorite:
- Final Ninja series (2 games I think?), 2D platformers where you could swing around and also shoot enemies with ninja stars. had a lot of levels to complete
- Dirk Valentine, 2D platformer, similar to final ninja but with a different theme
- Avalanche, a 2D game where you are a penguin trying to escape the avalanche by sliding and avoiding obstacles. I think this had a lot of levels too
Looks like nitrome has these flash games to download on their website, but they also converted / are converting them to html5 as well. I'm so glad these aren't lost!