I'm quite happy printing PLA with the Ultimaker 2 but I'm curious what I

I’m quite happy printing PLA with the Ultimaker 2 but I’m curious what I can achieve with other fancy materials. I already ordered some Bronzefil and thought about getting a spool of Ninjaflex. Any other interesting materials worth checking out?

In my opinion, you have not extruded a good plastic till you have tried Taulman’s line of engineered plastics. BUT I will say I am not sure if the ultimaker can handle the heat ranges.
NinjaFlex is a really great filament too, it is challenging to get dialed in but once your settings are correct you can make amazing things with it.