My favourite one is 10.3 Panther with the mix of aqua and brushed metal. 10.4 Tiger is similar but it has a glossy top menu bar that didn’t age well in my opinion. 10.5 Leopard has the fancy cheesy 3D dock, transparent top menu bar, and the more modern gradients. It looked great at the time but gradients aren’t as cool as brushed metal and aqua.
Everything after is a bit boring.