Modify View top10 to show top10 results from categories instead of the entire site.
If you are using the livesearch feature with K2,that is wp database dependent. You could try adding a google search box to your site with the option to search the entire site. That’s definitely the easiest thing to do. Styling is lame, but it will definitely return results for the entire site.
Is anyone willing to take on the challenge of rewriting Top 10 Post/View Plugin to be able to show the top post per category?
Or how about adding a “most emailed plugin” for WP Email?