To get started let’s look at the Crowbar as presented in the current 5E rules:
Using a crowbar grants advantage to Strength Checks where the crowbar's leverage can be applied.
Obviously the use of one in some circumstances requires DM adjudication, but a crowbar is super useful. Advantage to ANY roll is kind of a big deal. Someone in your party should have one of these.
So how can we home-brew the crowbar a tad? Well for one I would house rule they do the same damage as a club, and are not really an improvised weapon. Just ask Gordon Freeman in Half-life. It seems like something most dwarves would be familiar with, especially if they come from a line of miners. A well constructed crowbar would be useful in prying apart seams or just to break rock.
I would imagine the most coveted would be an adamantine crowbar. Which is interesting since the fabled metal was recently featured in Xanathar’s Guide To Everything:
Adamantine is an ultrahard metal found in meteorites and extraordinary mineral veins. In addition to being used to craft adamantine armor, the metal is also used for weapons. Melee weapons and ammunition made of or coated with adamantine are unusually effective when used to break objects. Whenever an adamantine weapon or piece of ammunition hits an object, the hit is a critical hit. The adamantine version of a melee weapon or of ten pieces of ammunition costs 500 gp more than the normal version, whether the weapon or ammunition is made of the metal or coated with it.
An automatic critical hit against objects? Sign me up! What if the dwarves took it a step further and crafted a Spearbar? All the benefits of being a lever, chisel and a nasty piercing weapon. This would be a tool/treasure worth coveting for any dungeoneer!
Below Youtuber Chasen Tom did just that minus the adamantine...I think!
I’m a big fan of mundane equipment as it harkens back to old school D&D. Descriptive play was the thing. We made good use of every tool at our disposal as we explored the dungeon. This was more then just consulting skills and rolling dice. Rather an invitation to be a better player, a better DM and ultimately a more imaginative gamer. I invite you to read over the adventuring gear section of the Player’s Handbook, you may be surprised at what you find!