Liberty BASIC. It's been around for nearly three decades, is very well documented, has excellent support, and is the closest you can get in modern times to the syntax of the original Dartmouth BASIC. So it easily appeals to the old-school crowd like me. But it also has over 300 commands or constants to keep up with modern operating systems and methods which allow for GUI design, event-driven applications, calling DLLs, playing media files, interacting with joysticks, displaying graphics, etc.