Here are some of the tools used in SharePoint Development. Let me know if you want to add anything to this list.
Visual Studio 2013 – Visual Studio is essential for any kind of development on the Microsoft platform including SharePoint.
Office Developer Tools for Visual Studio 2013 – This makes it very easy to connect to SharePoint Online by using the Connected Service option from the context menu
Web Essentials for Visual Studio – This is awesome free tool. It is helpful for doing client side development such as HTML, CSS3, Less, TypeScript, CoffeeScript etc
SharePoint Manager 2013 – It helps to inspect every site and property on your farm. A new online version is also released to inspect the SharePoint online environment as well !
SharePoint Client Browser – This is similar to SharePoint Manager online version. It can be used to remotely connect to your SharePoint farm or SharePoint Online and inspect the various artifacts such as hidden lists, properties etc.
Fiddler – It is a web debugging proxy. It allows you to see the request and response from your machine. It is helpful in tracing REST calls including communication between Workflow manager farm and SharePoint. It can be used to craft headers and REST queries and analyze the response such as raw data, json or xml.
ULS Viewer – It can be used to visually see the log file data instead of searching through the text log files.
CKS Dev for Visual Studio – A collection of templates, server explorer extensions and tools for SharePoint 2013 development.
SharePoint 2013 Search Query Tool – This tools helps you to build and test out REST based search queries. It can be used for both on premise and SharePoint Online.
Smtp4Dev – This is very useful when testing email functionality during development, when we don’t want to send actual emails to users.
SharePoint Color Pallete Tool – Specifically designed for branding SharePoint.
SPFastDeploy – A visual studio extension for quickly deploying changes to app during development. There is an option to deploy changes during save.
Postman REST Client – This is a chrome extension which helps you to craft the REST calls, configure the parameters and test the results before using in code
SPCop – A visual studio extension for analyzing SharePoint code for best practices.
ILSpy – This is a free dotnet assembly browser and decompiler similar to .net reflector.