Limp : pronounced limp .
Sorry couldn't miss out on that. Don't know the rule but cnoc seems to vary betwen the two but there are plenty of other gaelic examples of cn being pronounced cr . chno dearg , a hill above Loch Treig comes to mind . For a megalithy example ,stones that are used for mortars or mashing bait , often confused with cup marks are called cnotag anglocised and pluralised as crottachen (various spellings).