For Windows [main]:
WAMP - much better than XAMPP, easier and fast to use
Notepad++ - use it constantly
PHP Designer - hardly ever touched it
For Mac [my Hackintosh, also used often]:
MAMP Pro - over kill, i know.
Panic Coda - best thing happened to me in a long time
For Linux-Fedora on X [rarely used]:
LAMP - yes, i'm a lazy bastard.
VIm and
Kate - VIm is an over kill, Kate doesn't really cut it... That's why I don't use Linux.