Ok, this may be the strongest melee weapon in the game, considering just the weapon itself.
Highest damage and a fairly reasonable weight. This weapon can actually save you 2 points in alchemy (no need to add a bonus to physical damage or "to hit" yourself, since they come on it to start). It's not too bad to find in stores either - this one came from Durnore, and I've seen them in the final shop as well. You can also find just +4 damage versions and add in a further damage type instead of the to hit bonus if you like.
However, it happens that the Axe feat is rather underpowered compared to other options (at least in my opinion), which is why this Axe sits in one of my collection sacks instead of getting used. Instead I prefer this War Hammer:
Don't let the funny low "value" fool you, this weapon is awesome and can be reliably found in every play through of the game - you just need to be high enough level when you find the war hammer, and then of course you'll need enough alchemy skill to add the enchantments yourself. War Mauls are available for bludgeon as well, and can deliver slightly more damage if you have a good one, but for me it's not worth all the extra weight (15 pounds or more).
I'll add in a picture for one piece of armor too. This is another benefit versus weight trade off - scale armor is slightly less protective than plate armor for the hands (one point), but is about half the weight. Awesome if you're watching that casting limit on weight of gloves / weapon / shield. It can also be found with this strength bonus, which is a great benefit. Strongest material quality I've found it in is this Mithril example.
In all these cases I have enhanced the original item with at least one additional enchantment via alchemy.