From an interview
with Saito Morihiro
The founder once said jokingly that there were no better techniques than koshinage (hip throws) and that he never got tired even if he practiced them from morning to night. Kokyunage and koshinage, which were once regarded as basic aikido techniques, are now being taught instead as applied or advanced techniques. I think it is unfortunate that this may have become necessary in order to preserve the techniques of aikido.
To the best of my recollection, Nishio Sensei usually executed "koshinage" that were adaptations of judo (much like ogoshi). Kuroiwa Sensei created a unique technique that was actually an adaptation of a wrestling single leg.
John Driscoll has made an almost impeccable case
that koshinage, in the "classic" aikido manner, where nage's hips are perpendicular to uke's (rather than judo's parallel) is the single, solitary aikido technique that is not derived from Daito-ryu; rather, from Yagyu Shingan-ryu. This article is kind of buried on the Aikiweb site - it deserves to be highlighted, for it's meticulous consideration of a single technique (John is a high ranking judoka as well as aikidoka, by the way). It also is a prime illustration of how a study of history can actually illuminate proper practice.