I would like to be able to select 2 different features (geometry type and feature class does not matter) this tool would have two columns (1 for each feature selected). In these columns it would list out the attribute names and the value in them for the selected features. If you are comparing different feature classes some or none of the field names may match, but if the fields do match the tool would compare the values in them and easily identify if the values were the same. It could highlight the attribute names to show you where they are not equal.
So for example if you selected 2 road lines, and every attribute on them were identical except the Name, this tool would highlight Name to let you easily identify they are different rather than you flipping back and forth between the two features to find the difference.
In addition to that it would be nice to be able to transfer the value to update and make them the same.
So in the sample with the 2 roads. Lets say that the roads should have the same name, then there would be a button that would allow you to transfer the correct name to the other one. If there were multiple attributes that were not equal, you could pick and choose which ones to transfer.