Which naval vessels in history represented significant advances in technology or capabilities?

So many answers that I could go with in the previous responses, so I’ll limit mine to the platform I was most familiar with. I give you the Ticonderoga-class cruisers:

Built on the Spruance class destroyer hull, the Ticos saw the initial deployment of the Aegis combat system that provided battlegroups with enhanced anti-air coverage. The introduction of Mark 41 VLS system allowed for the ships to provide multi-role capabilities to the modern Navy. Battlegroup, inter-platform network systems controlled by (what was then in late 80s and early 90s) a state of the art CIC, they gave the Navy incredible power projection capability.

In essence, its power moved it from a stepped up destroyer to the last, true cruiser class fielded by the US Navy.

Ticonderoga-class cruiser