I really love all themes of:
Peak A Soul+ (Mirai Kanojo, Koisuru Natsu no Last Resort, Kanojo to Ore to Koibito to., Imouto no Okage de Motesugite Yabai., etc.)
Szak (Ikinari Anata ni Koishiteiru, Subarashiki Hibi, Himawari no Kyoukai to Nagai Natsuyasumi, etc)