Nichijou is probably my favorite anime to be honest. It's fucking hilarious.
This is the image on my phone case.
As far as K-On goes...I've been watching clips and a lot of it looks funny, but I haven't gotten as far as watching an episode. I was a huge fan of the song, 'go go maniac'...which I believe was written for that show. I wish I could find this amazing cover of the song, but it was removed from youtube.
and for the horror/supernatural/sci fi. It's really hit or miss. I feel like anime and manga too, is incredibly saturated with these themes. So either I get a recommendation or I randomly stumble upon stuff to read/watch. Berserk and Oyasumi PunPun are my favorite manga's. Berserk is dark as fuck, really nasty sometimes, but it's really well done. The art and landscapes are incredible, and this guy has drawn literally thousands and thousands of monsters without recycling anything. And Oyasumi PunPun was written by Inio Asano who's an amazing author. His slice of life stories are always so heavy....like 'makes things sad for a day or two' heavy. Nijigahara Holograph and What a Wonder Life(vol1 n 2) are also really good. I highly recommend those as well.