I have been taught many different kinds of ikkyo. My favourite is attacking the head. BTW I would add to the list the ikkyos done by going under the arm, and finishing facing the uke.
My style is Aikikai.
The most important thing for me in ikkyo is not what I do with my hands, but with my hips. It must be hip movement that is transmitted through the arm, and my arm must be an extension of my hips.