There are startling few greataxes out there. You can find several excellent greatswords, considering the setting, but not so many greataxes that I've seen. Pretty much just the ones that KenPen mentioned.
You -can-, however, do a lot to make a run-of-the-mill steel greataxe more impressive. The recent addition of alchemy has broadened the availability of alchemists fire, and various other nifty yet damaging adhesives for your weapons. Alchemists fire alone provides a +1d6 fire bonus. I heard mention of acid varnishes (the logic of that is flawed, but hey, who cares in a fantasy setting) that could also give you another stacking damage type. Holy water can provide a +1 vs. undead, albeit temporary, to any weapon. And there are always the enchanted polishing rags, those add a temporary +1 enhancement bonus to about anything. Or enchanted whetstones, which give temporary keen.
Of course, the downfall is you are shelling out a lot of money for these temporary benefits. And you can't squeeze more than a +1 attack or enhancement bonus out, which means there are lots of foes out there which will shrug off your blows and laugh at you. But you can do a lot to turn a non-magical steel greataxe into a destructive weapon, still yet.
All that aside, greataxes, and a few other weapons, could do with a look at. I don't even know of a magical mace in the game (not that I know everything), and you can't tell me a mace isn't one of the most basic weapons around.