I posted this as an answer to another question, but after some thought, I think it qualifies as a feature request in its own right.
I would like to see a per-tag breakdown (based on a question's tag list) of each answerer's reputation in addition to their lump sum reputation. Something like this:
Question is tagged with:
C# winforms combobox
An answer would look like this:
Blah blah blah
Eric 200 C#170 winforms50 combobox10
This would give more insight into how credible a person's answer is. I think it will also be more rewarding for people that are more active in less popular tags. I'm not sure how difficult it would be to implement though.