Davaar Island is the best small adventure from Campbeltown: a tidal island reached across the Dhorlin shingle causeway at low tide. The walk gives you views back over the loch, then carries on toward caves and a Stevenson lighthouse.
The oddest sight is a cave painting of the Crucifixion, first made in 1887 by local artist Archibald MacKinnon. Check the tide times carefully; this is not a walk to improvise.