If you haven't already noticed, I like flex nibs. Especially Waterman flex nibs. Especially this Waterman music flex nib. I also really like Sailor Jentle Sky High ink and I'm really bummed that Sailor discontinued it (and I am skeptical whether Souten will be a replacement for it. Le sigh.).
I love this nib because it really highlights the shading and sheen of just about every ink I've ever used with it so far. Also: crazy delectable ink pooling.
Check out my review of the music nib here, as well as my music nib post if you're curious about music nibs!