Nickel is a metal that, in particular, seems underutilized in DF. It is a metal that has had a long history of being part of alloys with Iron in particular, and Copper, and one such alloy - Meteoric Iron - is prevalent in fantasy settings. I am aware of larger metal inclusion suggestions, but Nickel in particular should get some new ores and alloys.
1.) Pentlandite Ore is a new Iron Nickel ore that occurs close to the surface in sedimentary and soil layers, and in gabbo layers. It produces 4 bars when smelted: at least 1 iron and 1 nickel, and the other two will be randomly iron or nickel.
2.) White Copper (or Cupronickel) is an alloy made with 3 Copper Bars and 1 Nickel Bar. It has a higher concentration of copper than Nickel Silver and no Zinc requirement. Cupronickel is weapons grade, between Copper and Bronze.
3.) Ferronickel - Ferronickel is an Iron Nickel 1:1 Alloy. It can be smelted directly from Iron and Nickel Ores, from Pentlandite directly, or from bars. Ferronickel is weapons grade - between Iron and Steel.
4.) Nickel Steel - Nickel Steel is made in a similar process to steel, but requires a Ferronickel Bar in place of the last Iron Bar in the process. It is slightly stronger than steel for edged weapons, but not by much, about 20% more valuable, and has a higher density than steel.
I was considering stainless steel, but extracting cobalt from Cobaltite is a process out of reach for dwarves - but dwarves can extract nickel, and can alloy it into Nickel Silver already. It would be nice for the presence of Nickel on a map to make your copper and iron industries a bit more varied.