In the low-level front, I've used Assembly, C, C++, and willing to learn Rust or D, or Vala.
These days all my new code is written in F#, although I still need to touch a lot of C# code.
And I'm willing to learn TypeScript or Elm in case I need to do some web+frontend development.
Or Ceylon/Kotlin (along with RoboVM if iOS is needed) or Swift (when it becomes opensource), in case I want to do mobile apps.
In regards to databases, I'm an old-school guy who thinks normalized data usually beats any NoSQL solution, except for rare BigData cases.
If you require consulting work, I'm generally available for hire.