I'm sure our Scottish colleagues will be along shortly, but having been a tourist a few times, I can recommend:
OBAN area:Personally, I prefer Oban as a good base. Fort W is less interesting (IMO) but is just up the road. The distillery tour at Oban is good too.
Trip on the boat to Mull from Oban (40 mins) where you'll see the castle Duart featured in the film Entrapment (Connery and Zeta Jones) Need to take the car if you want to see the island.
Also the picturesque town of Tobermory.
Short boat hop to Iona to see the monastery - if you like that kind of thing. I did.
Glen Coe is close by - lovely scenery.
The walk up the Nevis Valley is fairly easy, and is stunning, so no need to climb the big one.
Cruachan Power station does tours - it's hydro electric and you get to go inside the mountain which is cool.
SKYE/ TorridonFurther up the coast you have Isle of Skye (with road bridge) and the amazing Cuillin Mountains. Also, on the mainland, you have the spectacular Torridon Mouintains which are great.
The Kyle of Lochalsh has Eilean Donan castle which is worth a visit.
Often good seafood in the area too.
So much to see. Knoydart (remote place) via boat from Mallaig is a good trip.
Fishing available at many places too, if you like that kind of thing.
Further south of course, you have the Isles of Jura and Islay, famous for their whiskey... so a potential boat trip for a distillery tour.
That should do for starters !