I suggest small graphical icons (~16x16) with distinctive colors and sillhouetes. Maybe:
A gray X over a black dollar sign for Free
A green exclamation mark for Easy
A yellow yield sign with an exclamation mark for Memetic Hazard (like your lightbulb one, but probably a lightbulb shape would be too small to make out at reasonable icon size).
It would also be good to arrange the icons and entries in a table, so that a given icon always appears in the same column.
I suggest small graphical icons (~16x16) with distinctive colors and sillhouetes. Maybe:
A gray X over a black dollar sign for Free
A green exclamation mark for Easy
A yellow yield sign with an exclamation mark for Memetic Hazard (like your lightbulb one, but probably a lightbulb shape would be too small to make out at reasonable icon size).
It would also be good to arrange the icons and entries in a table, so that a given icon always appears in the same column.