At the moment, my favourite opening is Re:Do by Konomi Suzuki (Re:Zero) and Styx Helix by MYTH&ROID (also Re:Zero).
Although, a few runner ups for the OP are Koutetsujou no Kabaneri by egoist (Koutetsujou no Kabaneri), Paradisus Paradoxum by MYTH&ROID (Re:Zero) and Kurutte Hey Kids! by The Oral Cigarettes (Noragami Aragoto).
For the endings, it would have to be LLL by MYTH&ROID (Overlord), Sore wa Chiisana Hikari no Youna (Boku dake ga Inai Machi) by Sayuri and Zetsubousei: Hero Chiryouyaku by Soraru (Danganronpa: The Animation).
Yes, I know the MYTH&ROID bias is extremely obvious, but I just really like their music. Also for Re:Zero. But, to be honest, Re:Zero is one of the best anime out there, along with my personal favourites. But from a critics view, Re:Zero is almost a god.