Some v good shouts on here at either end of the journey and at points in between. I'd echo Ally's thoughts on Sutton and St Anne's, and also throw in a mention for the clubhouses at both, which make excellent use of their locations. In the bar at Sutton in particular you feel like you are almost out in Dublin Bay (though that could be the lively membership factor as well).
If quirk is your thing, in the same neck of the woods I'd also throw in a mention for the heathlandy Howth GC, on elevated land around Howth Head, and a James Braid design (I would guess still bearing a lot of the original imprint). Lots of elevation change, blindness and doglegs like they just don't (or can't) do any more. The 5th in particular is a dogleg you won't believe (think of trying to go up a helter skelter and you get a sense of it).
There was a mention of Kirkistown above - a v fun links (incorporating the unhittable par 4 10th as SI 1) but a bit of a detour. The Ards Peninsula is lovely though so if you have time do consider this one. One option would be to take in the Annesley at RCD (and / or Ardglass, which is even closer) and then make your way to the little ferry across the bottom of the lough at Strangford - brings you over to Portaferry which is then just 15 / 20 mins from Kirkistown. Wouldn't be a bad 36 (or 54!) that actually.
Whatever else, the one I wouldn't miss out of all those mentioned is Portrush Valley. A must.
Enjoy!