Looking for something that is well laid out & easy to read.
As I understand it, since a Heuristic Evaluation report would show data collected from multiple sources and an aggregate of that data, the simplest format would be a bar chart with overlays.
Having said that, I think adding some design approaches common in infographics might go a long way towards improving legibility and adding impact. While these examples aren't specifically tied to Heuristic Evaluation data, the approach would translate fairly cleanly.
http://www.flickr.com/photos/bartclaeys/3351321706/sizes/o/ (I especially like the circular bar at the bottom.)
http://www.dominicforest.name/wp-content/photo_visualisation/graphical_text_similarity.jpg (A bit more abstract.)
http://www.dominicforest.name/wp-content/photo_visualisation/flare.jpg (Even more abstract.)
I think I would approach a report display by using vertical height to represent positive/negative heuristic value, horizontal value to be the categories evaluated, and colors to indicate either strength of compliancy or to organize sections of the report by sub-categories if there are a significant number of categories.
Hope this helps!