On an elliptic curve over $\mathbb{Q}$, we can associate a canonical Neron model and with it a Neron differential, whose coefficients in some natural coordinates yield the Dirichlet coefficients of the L-function (or the coefficients of the associated modular form, as you prefer). Is there a similar story for K3 surfaces? I envision a canonical integral model and a section of the canonical bundle such that it is related to the automorphy and thus the L-function of the weight-2 part of cohomology in a simple way.
Maybe there's even a similar story for more general Calabi-Yau varieties? I am more skeptical of this.