GAMEMAKER IS not FREE

[Koh]

A note about gamemaker: it doesn't require programming (per se)
there are drag n drop commands that are really useful for starting out with, while still teaching concepts useful should you ever decide to start using code instead (which, admittedly, is more powerful)

This basically. The Drag 'n' Drop (DnD) will only get you so far. Learning the programming language is absolutely required if you want to get the most out of the program. Everything I've needed it for thus far, Game Maker has been able to do with its programming language (GML), which is like, the lovechild of Java and Delphi. You can also extend Game Maker's functionality with the use of DLLS written in C++ or such.

One thing Game Maker doesn't support as of this moment are palettes. So if you have a sprite of a guy that will change from blue clothes to red clothes, for example, you'll have to make separate sprites/spritesheets for that, or make clever use of code and blending of clothing sprites that are drawn above the original clothes.