As others have said, Arran, Mull of Kintyre, Islay, Jura, Moidart, Etc, etc. all fantastic.
There is a foot ferry (a big RIB) from in Antrim to Campbeltown . The trip across in itself is worth it. I did it this summer in flat calm conditions. We were skimming along at 30+ knots between Scotland and Ireland with dolphins rising either side of the boat.
The ride up Kintyre from Campbletown is lovely and gives you loads of options to branch off at the top.
One key difference between Scotland and the rest of the uk and I guess Ireland is that wild camping is possible. Just be careful of the ticks in moorland areas.