These are my personal favourites right now:
Very versatile text editor for all programming languages with a variety of plugins and skins that can be installed through Sublime package installer.
Just a MySQL database GUI for when you need it although working with command line is usually faster
FileZilla FTP client
FTP access to your server is a must have
Command Line (Preferably Mac/Linux)
Unix command line is my favourite tool for almost everything. Learning to use it effectively makes life a lot easier and you also need it to SSH to your server.
Local server for development.
LAMP-Linux (Apache, PHP and MySQL can be installed separately)