I have very fond memories of Katawa Shoujo, even though it wasn't my first VN. I remember great, often very soothing music and kind of comfy (?) atmosphere. Also, the characters were quite memorable and well written. For some weird reasons some switch got flipped in my memory, and in my head I remembered the voices of the characters even though the game was unvoiced
For me this is one of the true gems, not only for OELVN, but among VNs in general.
This, together with The Language of Love is one of the very few OELVNs (perhaps even the only ones) that managed to convincingly pull off the japanese setting. I even remember some people on the forums believing that KS was translated JVN
My favorite routes and heroines were Lily and Hanako.