And if you need something even lighter, something like a better Notepad is enough. Lightweight text editors are a dime a dozen, but I'm personally a fan of notepad2 / notepad2-mod / notepad3; even if they don't have tabs.

Also shout out to LINQPad, for letting me test quick snippets of C# with better visualization than Visual Studio. It's also a better alternative to Sql Server Management Studio for running SQL.