Castles: Caerlaverock, Stirling, Edinburgh, Eilean Donan, Hermitage, Bothwell to name but a few.
Palaces at Scone, Holyrood,Falkland and for the medieval enthusiast Linlithgow.
Battlefields: Bannockburn, Killiecrankie, Flodden(in England just), Culloden.
: Edinburgh... take your pick!
Tour of the old city underground, the ghost walk, Royal Yacht at Leith. walk the Royal Mile.
Other places to visit: Burrell collection and Art Galleries & Transport Museum and Science Centre all in Glasgow.
Towns of note and beauty: Stirling, Perth, Pitlochry, almost anywhere in the Borders, St Andrews, Inverness.
Scenery, honestly, hard to beat on a good day anywhere in the world. West coast from Glasgow (north) to Sutherland will simply take your breath away.
Visit: Glencoe, Rannoch Moor, Loch Earn, Moidart, Skye, Jura, Iona - graveyard of 30? Kings and Viking chiefs and home of St Columba's monastery.... I would avoid:
The outer Hebrides, nice but too long a journey for gentle low lying islands.
Now Golf courses......................
Dannie and Burkhard.... Google a quarter of this stuff and you'll be busy for a week or more...