I’m just listing down the Top 10 Exchange Tools:

• Exchange Mailbox Server Role Requirements Calculator – Provides output on your storage configuration as well as backup and replication requirements.
• Exchange Remote Connectivity Analyzer (ExRCA) – This GREAT tool allows Exchange admins the ability to validate their Client Access Service configurations (EWS, Outlook Anywhere, ActiveSync.) and SMTP functionality via an online tool; very useful in testing and troubleshooting.
• Exchange Client Network Bandwidth Calculator – Forecast network bandwidth requirements based on the number of and type of Exchange access client used by this tool in graphical form.
• MFCMAPI – Provides access to MAPI stores through a graphical user interface. Its purpose is to facilitate investigation of Exchange and Outlook issues (see examples here) and to provide developers with a canonical sample for MAPI development.
• Exchange Server Deployment Assistant (ExDeploy) – An online tool that walks through deployment options and generates custom instructions for moving your organization to Exchange 2010 or Office 365. Gives a good general idea of the steps and requirements for deployment based on your input.
• Microsoft Exchange PST Capture – As many organizations move to Exchange 2010 with archiving data policies take on greater importance. This tool will allow administrators to discover and import PST files directly into their Exchange environment.
• Calendar Checking Tool for Outlook (CalCheck) – A good tool for checking for calendar problems within a specified mailbox. It performs various checks on general settings, such as permissions, free/busy publishing, delegate configuration, and automatic booking.  This tool can be used diagnose issues or identify trends.
• Microsoft Outlook Configuration Analyzer Tool (OCAT) – As with the CalCheck tool this tool provides a quick and easy method to analyze Outlook profiles for common configurations that cause problems providing a detailed report of the current Outlook profile and mailbox. This report includes many parameters about the profile, highlighting any known issues.
• Microsoft Active Directory Topology Mapper – reads Active Directory configuration using LDAP, and automatically generates a Visio diagram of your Active Directory and/or Exchange topology. The diagrams may include domains, sites, servers, organizational units, DFS-R, administrative groups, routing groups and connectors and can be changed manually in Visio if needed. Very useful for getting a head start on creating a detailed diagram of your environment.
• Microsoft Exchange 2010 Visio Stencils – As implied contains a Microsoft Office Visio stencils with shapes for Microsoft Exchange Server 2010 and later.