There is a RANK tool in Raster but often as I am teaching GIS to others Ioften find they want to create a rank of a field (say they are creating habitat suitability models or other data, I find that they want to create a field to rank something like Area_km2 for their final outputs) and then symbolize it.
While you can sort that field, that only gives a visual of column. Most folks who ask about how to do this want to symbolize their data further for cartographic layouts.
The thought of this tool would be that you could choose a field (or field), choose a sort option and then output a new field called "Rank" to provide a ranking order of 1 to x. Normally the solution I provide is external to ArcGIS -- Download the table, open in Excel, Sort Ascending/Descending, Add a column called rank, add 1 to the top most, then add a formula of the cell with 1(i.e. C1) so C1+ 1, drag that formula down through the data, Save as CSV and then rejoin the data. Most of the folks I work with are not comfortable with editing/writing scripts. I think this would be a fairly easy and useful tool for a number of folks.