There are a lot of songs i've never heard.
teens
Sotsugyo Shashin + the rest of A Ballads excluding Rainbow
Most of A Song For XX except for Depend on you, Whatever, and Poker Face
Also I had never heard most of LOVEppears until like a month ago when I actually decided to listen to it all the way through. I'm in love with it now
Also any remix albums like ayu-ro-mix 1 & 2, ayu-mi-x 3, ayu-mi-x 4, which I would say is unusual for me because I love her remixes.