XTools Pro is one of the most popular and full-featured extensions for ArcGIS Desktop.

Originally developed as a set of useful vector spatial analysis, shape conversion and table management tools for ArcView GIS 3.x. XTools extension was then converted by Data East to ESRI ArcGIS environment and now is re-designed, enhanced and extended as XTools Pro to get to the newer level of functionality and performance.
Latest version – XTools Pro 5.1
XTools Pro 5.1 is a minor upgrade introducing following new and updated tools and features for ArcGIS users:
Windows Vista compatibility
Windows Vista compatibility
- XTools Pro 5.1 is now compatible and can be used with Windows Vista operating system
Split Polygons
- a new tool for splitting polygons is implemented
Extract Map
- a new option for outputting extracted maps to .mxd format is implemented- a new option allowing renaming long attribute fields when extracting from geodatabase to shapefiles is added- a new option for silent extraction requiring no user interaction is added
Export Data to KML
- exporting to KMZ format is now supported- a bug with exporting point layers symbology is fixed- a bug with exporting "Null" values in geodatabase feature classes is fixed
Find Duplicates
- a new option for removing duplicates is introduced
Export Table to Text
- non-English names for output folders are now supported- text files can be output in ANSI, UTF-8, and UTF-16 formats
Callout Identify
- now you can select a layer that will be processed by the tool
Calculate Tool
- new measure units added
Import Data from KML
- input KML/KMZ files are now not deleted after processing- the tool is now compatible with ArcGIS 9.1
MultiDelete Fields
- progress bar is added
Identify Pro
- related tables are now correctly supported- improved performance when working with related tables
Create FeatureClass/Table
- a bug with creating new feature classes in ArcGIS 9.1 is fixed
Other changes
- XTools Pro 5.1 provides new 30-days trial period for unregistered users- Minor bug fixes and enhancements
ArcGIS compatibility
- XTools Pro 5.x version is compatible with ArcGIS 8.x/9.x
NOTE:
- XTools Pro 1.x licenses are not valid for XTools Pro 5.x- XTools Pro 2.x licenses are not valid for XTools Pro 5.x- XTools Pro 3.x licenses are not valid for XTools Pro 5.x- XTools Pro 4.x licenses are not valid for XTools Pro 5.x
From : http://www.xtoolspro.com/