I have many favourites in my mind and I can't choose but the first one I loved was the 1st opening of guilty crown (my dearest). generally I find egoist and supercell songs really nice.
I love lots of openings, titles are: -Click (Nisekoi) -Ideal White (Fate Stay Night) -Dead End (Mirai Nikki) -Contrail (Ao no Kanata) -Bravely You (Charlotte)
assassination classroom season 2 both openings, hunterxhunter, your lie in april 1st op, kiseijuu, re:zero 1st op, noragami season 2 op, shokugeki no soma season 1 op 2 & season 2 op 1, ushio to tora season 1, soul eater black paper moon (to lazy to look up which 1 that is) and one piece hard knock days