When in Scotland, do as the Scots do. Drink whisky.
So whether you're a fan of whisky, or maybe of tours based on alcohol, I'd highly recommend taking a tour of the Macallan Distillery. It's only 5GBP for an hour and a half tour, which includes two tastings of their whiskies.
My favorite part was the aroma hall, which you could sniff all the different subtle smells of a whisky- the fresh fruits teardrop was MOUTH WATERING. I'm salivating now just thinking of it.
They also have some incredible whisky-based goodies, such as ice cream, mustard, fudge... delicious, oh my!