A few places I like in Bretagne :
- The Mont St Michel bay is nice but really too crowded, to be visited at undue hours (sunset eg, sunrise is not as nice but quieter),
- This applies to a lesser extent to the old town of St Malo, with nice surroundings too,
- The most beautiful coast of this area is the Cote de Granit Rose (Pink Granite Coast) between Paimpol and Perros-Guirrec or Treberden, with very scenic places such as the Sillon de Talbert or the Bréhat island (access by boat from Lezardrieux or Paimpol).
- South of the Brest haven, Camaret and the Cap de la Chèvre and Pointe de Pen-Hir are nice, and farther south the Raz de Sein (Pointe du Raz) can be quite scenic too.
- I know the south coast (Bretagne Sud in french) better from the sea (sailing) than from the shore, so wouldn't be very useful, but I'll suggest Concarneau (nice little haven and departure for Glénans), and Etel, Auray and LarmorBaden for their rias. Quiberon is quite worth a visit too, in this area.
It's not as practical if you travel by car, but every island can be worth a visit.
The accessibility of some of them can depend on the weather, as testify the seamen' sayings (qui voit Groix voit sa joie, qui voit Molène voit sa peine, qui voit Ouessant voit son sang, qui voit Sein voit sa fin, I'll let you translate ).
Add the Glénans (south of Concarneau) and Houat & Hoedic (south of Quiberon) in the south coast, who can show a bit of a Carribbean mood if the weather is with you.
There are of course many other nice places that I don't know or didn't think! Particularly, I didn't speak of the inland, which can also have some rural charm in some places but has more often often been damaged by intensive pork and grain farming.