For some reason I can't upgrade some weapons and armor past Flawless or Epic. I have a smithing of 100 and even tried it with Notched Pickaxe equipped for a possible bump in smithing past 100 but no dice. Can anybody help me?

Do you have the appropriate perks for the type of weapon you are trying to improve? Glass, Daedric, et cetera. Without the perk, it takes something like 170 Smithing skill to get a piece of equipment to Legendary.

Yeah my smithing tree is maxed out. I have everything. But certain items won't let me even touch them. Keening and Ebony Blade are shining examples of this. Mehrunes Razor I can't even upgrade near Epic, forget about Legendary. Which leads me to think why even have something in the game at all if it's so weak around level 50 it isn't even the slightest bit useful?

From the wiki: Though every other Daedric artifact weapon is able to be improved through smihing, the Ebony Blade is missing the required data to be tempered at a grindstone. It is also missing a classification for weapon material, preventing it from benefiting from smithing perks, if ever a smithing option were introduced.

Doesnt mention anything about Keening, but it says Mehrun's Razor is upgradable.

Odd. I could upgrade Blade of Woe to Legendary without Daedric / Ebony perks or any potions at all, with about 60 Smithing. I thought it was suss, I could only upgrade my Elven to Exquisite even with appropriate perks...

I figured this would be something fixed in a patch by now.

Enchant some equipment and make some potions to get your smithing past 100. It does count.

Upgrade them to Epic or Flawless. After that. Go back to Grind stone or Workbench and drink Blacksmith potion. Which I have seen 2 types (Philter 30%and regular 20%). Then you should get the Legendary option. I have done this with Orcish and Elven
Armor and weapons. Have not made any Ebony yet.

I forgot to add. My level in Smithing is 86

Arcadias in Whiterun sells 50% Blacksmith potions, not often but they are there sometimes, I just go in there wait 48 hours if there's no 50%, better for me that faffing around with alchemy to make smithing potions.

You can also find various bits of jewelry and armor with smithing bonuses: bracers and gauntlets, rings, necklaces, etc. and you can also enchant clothing with a bonus, too. It all stacks up.

All you wanted to know about http://www.uesp.net/wiki/Skyrim:Smithing.

And all about items with http://www.uesp.net/wiki/Skyrim:Generic_Magic_Apparel#Fortify_Smithing.

Actually 1.4 nerfed smithing on my 360. I can't upgrade Skyforge Steel Swords anywhere close to where I was able to on Tuesday.

1) You can put the Enchant Smithing enchantment on rings, necklaces, gloves, and chest pieces. They all stack with each other. Unfortunately the Notched Pick Axe will not stack with these effects, so don't bother.

2) You can magnify (1) by consuming a "Fortify Enchant" potion before you make that gear.

3) You can magnify (2) by creating the potion with already Fortified Alchemy gear.

Once you've done a loop or two of (2) and (3), you can create a Fortify Smithing potion (or just buy a powerful one from Whiterun's alchemist). That plus your fortified Smithing gear built with Fortified Enchanting potions will cause you to have ridiculous smithing skill.

How ridiculous? Preposterously ridiculous. Ludicrously preposterously ridiculous. You'll be making weapons that can one-shot most (if not all) encounters.

I don't think you need to upgrade them first.

There are a couple items that never show up on the smithing, like the Horned Scale Armor or Supple Ancient Nord Bow. Bothers the heck out of me.

My Smithing is around 80 and with the Smith potion I was able to make everything I have (Plate Steel, Scale Mail, Glass Bow, etc.) Legendary. I do have the perks also.

Some weapons are affected by the perks that allow you to upgrade weapons twice as much even when they aren't obvious. For example, Skyforge Steel weapons will be better tempered when you have the Steel Smithing perk, even though you can't make them.

Mehrunes' Razor is not affected by any perks. Nor are Iron weapons and a variety of others.