I work & stay all around Wales and would say that Conwy, Llandudno & Llangollen are up there. Porthmadog is also one of my favourites..... nice curry house & a bookies! !
For quaintness, there a village east of Porthmadog, Beddgelert, which is smart.
In the south, I would recommend Narberth & Crickhowell.
Rhyl, Prestatyn & Merthyr all all pretty dire though.