I have used this 2 editors only:-
Notepad++ (https://notepad-plus-plus.org/download/v6.8.3.html)
TIP, Goto Language in the toolbar, select C, then C++ (or) select S, then select SQL
Sublime Text 3 (http://www.sublimetext.com/3)
TIP, On the bottom right cornor, there should be a text named 'plain text', it may differ, click on it, select D from the list
Hope that helps you, if u know more, post here, I'll update this
Don't use C++ for squirrel. On Sublime Text there's this awesome syntax highlighter called "d"
Just press CTRL + SHIFT + P then type ssd
Thanks, tried it. IT's really awesome, UPDATED
I like to use the SQL language in Notepad++ to edit.
I just use the standard notepad, the console lets you know about syntax errors.
UPDATED!, Thanks
@MatheuS for telling me about SQL