Just felt like posting this here because it's something that apparently some people don't know about, and I have no idea how I would work in Unity without it.
When messages show up in the Console, if you select a message, the window beneath the console will show the complete call stack, with line numbers for where the call occurred. Line-by-line debugging in Unity sucks, so this is the next best thing.
This has loads of applications beyond finding the lines causing bugs. If you want to know where a variable is being modified from, you can wrap it in a C# Property, then make the variable private so it can only be accessed via the property, then put a Debug.Log() in the property's Get function.