Edit: i realized i was slightly off-topic and a little incorrect.

so, my musthave's:
blender
+
paint shop pro 5
+
gs

but blender's my biggest one. if i didn't have gs, i'd find something else (probably irrlicht, coz atm i wouldn't want to spend money on something besides gs), but blender is fantastic for heaps of things. it destroys windows movie maker when it comes to home-movie editing, and so i'm using it with a few of my mates to make a fight movie during my free periods at school. and of course, it's a fantastic modeling tool.

julz