I am good at low level programming and dwarf debug format, I have written a java library to parse dwarf directly, this prove my skill set is not bad.
I don't know there is room for me to contribute on this part (debug format) for Rust. Dwarf has some weak points. If Rust can use a new debug format, it would be interesting and I would love to contribute it.
I think it would be great if someone could work on GDB or LLDB so that they can support evaluation of Rust expressions for example. Basic support could be done with no change to debug information rustc currently emits.
To echo @sanxyin the highest-impact project is probably teaching either GDB or LLDB directly about Rust DWARF so that we don't have to pretend to be C and pretty-print GDB's C output back into something that looks like Rust.