I just hit a high enough level to gain access to 5th level spells. 

I've been considering 2 primarily. Cone of Cold looks worth the slot as an offensive spell, but I also like bending the game to my will, so I am looking at the creation spell. 

Aside from the obvious uses of manufacturing counterfeit goods and currency to trade and sell to merchants, what other uses are there? Could I, for example use the spell to create, say a mundane simple or martial weapon such as a Dagger or Shortsword, or a set of plate mail armour for a Fighter? 

Yes I believe you can use it to create mundane weapons. 

At 5th level, you can use Creation, to create doors, wall to block passages, duplicate keys...

At higher level, you can use it to create passages, like bridges or similar...or barricades.

Dropping a 5x5x5 lead cube on an enemy from 30 feet.

The casting time is one minute, good luck surprising anyone with that. "Huh, that wizard sure seems to be casting a really powerful spell and there's swirly bits of arcane matter forming above my head. I'm sure it's nothing."

Quote from Twooshort >>

The casting time is one minute, good luck surprising anyone with that. "Huh, that wizard sure seems to be casting a really powerful spell and there's swirly bits of arcane matter forming above my head. I'm sure it's nothing."

hrm... you don't play with people who can coordinate plans? like "hey... I'll make this cube here. you go grab their attention, and lead them back here."

Just, run in and fight huh?

I had the idea of using it to make a 5x5x5 chunk of critical mass uranium, plutonium etc. If you put them into glyphs of warding, fill up the entire range creation can go to, etc and time it, you can basically exterminatus a planet.

Quote from Cypher3065 >>

I had the idea of using it to make a 5x5x5 chunk of critical mass uranium, plutonium etc. If you put them into glyphs of warding, fill up the entire range creation can go to, etc and time it, you can basically exterminatus a planet.

 
Given that the spell cannot create these, I'm guessing you have a very generous DM. 

I have yet to try this, but figured it might be considered either stone, being an ore, or a precious metal. I suppose you could do the same with a trip to limbo or wish if the DM doesnt agree.

Precious metal only includes gold, silver or platinum or basic metals like copper and iron. 

You cannot create rare materials beyond those defined by the spell. You are also limited only to the materials you have seen. So unless your character has seem the form and material of plutonium, uranium or whatever, you cannot conjure it. 

There is nothing stating these materials exist in Limbo. 

This use of wish will have significant consequences on you plus you will need to be careful how the wish is worded. This also requires two things: that your character has a detailed knowledge and understanding of the material and that this material exists in the campaign world while being knowable and named. 

So no matter what, if DM disagrees it will not happen. At all. And you're either in a whacky game or have a whacky DM to just hand you such materials whenever you want. Personally, if your aim is widespread destruction, some good use of Meteor Swarm will do the trick - the damage and wide area means you can destroy a village with a single casting. Not a nuke, but it'll make an impact. (puns)

In limbo you can make anything, so long as your character is intelligent enough to control it, also the hermit background gives you some revelation, maybe you could get atomic theory from that? If curious enough they might use the place like we do particle accelerators, making each element until they hit something radioactive. Also I get that this is something no sane DM would make possible, much less allow you to do unless there are story strings or something similar attached, like there was a quest over it or maybe it was the BBEG's plan. I think its still possible but concede that it is MUCH harder than I initially thought. 

It seems to me like Wall of Stone is probably just as good or better than Creation in combat circumstances.  It doesn't take nearly as long to cast and it creates more material.  You can make a bridge, a ramp, a blockade, or "ladder."  Creation seems to be more a sandbox game type of spell.  It's the kind of thing you want if you want to spend downtime crafting things all the time or finding fun ways to mess with the heads of your rivals/enemies.  

Not gonna lie, doesn't specify that you can't make magical things with creation. Maybe your rogue wants to take out some strong enemy and they just have some daggers. Even more, you can't afford those nice +3 scimitars you saw in the shop.

Oh wait, give the rogue 2 +3 scimitars for a certain duration before fighting a boss.

Creation only creates matter, it doesn't create any enchantments. And rare materials like adamantine and mithral doesn't have any inherent +hit/+damage like they did in 4e.

sorry for necroing this but just had to say this is a Awesome spell in combat as an lvl 6 illusionist, make a piece of hemp rope (1 day duration) then give it to a flying familiar and fly up high and then use Malleable Illusions to make it a 5ftx5ftx5ft cube of adamantine  and drop it on a enemy... Bam dead enemy 

im going to assume vegetable matter also means any plant really witch mean theoretically you could summon up a pile of the worlds most deadly plants. or need a rare herb? for a potion? boom of course it gets a bit murky when you question how real the actual properties of the plants are like would the bay leaves you summon taste like bay leaves and flavor food like bay leaves; if made into medicine or healing potions are they going to go inert at the 24 hour mark? or is it simply a replica nothing more than a plastic flower (so to speak)

and on the other side of things you could make boats OR Trojan horse style objects that formed around you so they are seamless.

and dont forget that while it does say ("an object" i assume that means only one item can be made)they could be all connected by toothpick style sticks that are easy to break like model kits

Actually uranium is a precious metal. Plutonium isnt tho

The 1 minute casting time of this spell makes it rarely useful, and the requirement of a sample basically makes it worthless most of the time.  Fabricate rarely needs special materials. 

The real problem with this spell is that Animate Objects and Bigby's hand are just so very very versatile.   Animate Object in particular can carry objects, break other objects and do so many many non-combat things.

Need to activate a trap without getting hurt?  Send in  a feather duster.   Need to cross a cavern, instant flying chariot.   Need to get through a locked door?   Animate the LOCK.   Need to block a passageway, animate a boulder or two.

The only way I would take Creation is if I was some kind of Craftsman wizard rather than

Quote from Mog_Dracov >>

The 1 minute casting time of this spell makes it rarely useful, and the requirement of a sample basically makes it worthless most of the time.  Fabricate rarely needs special materials. 

The real problem with this spell is that Animate Objects and Bigby's hand are just so very very versatile.   Animate Object in particular can carry objects, break other objects and do so many many non-combat things.

Need to activate a trap without getting hurt?  Send in  a feather duster.   Need to cross a cavern, instant flying chariot.   Need to get through a locked door?   Animate the LOCK.   Need to block a passageway, animate a boulder or two.

The only way I would take Creation is if I was some kind of Craftsman wizard rather than

 You missed my favorite: Get attacked by a wearwolf, animate a roll of SP. 😂

This is an illusion spell if your illusion wizard you can change the shape and form of it  With an action have it be a tiny pebble and then user action Make it a five-by-five wall or whatever you want lasts 12h if stone lol