In reply to walkywifelet:
Normal "it depends on conditions on the day" caveats inserted, but.....
Coyles of Muick by ballater could be a good option - relatively low lying, distinct top and most terrain above tree line is flat(ish) bar the summit it's self. Lovely views down deeside and into the main Corrie of lochnagar.
Glen tannar is lovely for a wander as well.
If conditions underfoot are benign the a walk up to the dubh loch from glen muic is also nice and the crags on the other side of the loch magnificent to see in winter.
Depends on which side of the city you are on, but bennachie / millstone can be nice if snow stops play for you for higher tops etc.
Clach na being as mentioned earlier by someone is nice as well.
Cheers,
Stu