A very quick and simple fudge dice (+, +, -, -, blank, blank). They are designed to be used with roleplaying systems like the awesome Fate system: http://www.faterpg.com/. The indents can be a bit hard to see, so I now use white PLA and fill in the lines with a fine point permanent marker (the colour often bleeds a bit). As they are hollow, I also like to drop a small round bell into them as they are printing. It gives the dice a bit more weight, more randomness and a nice sound.
I use this as a test cube for my printer (if it works I have a new dice, if it doesn't I can see where it went wrong.) They often come out about half a mm off in height and width. They use about 1gram of filament and take about 10minutes to print.
The native scale is very small, but I have printed it from 10mm to 22mm without issue.
I have used PLA to print this at 0% infill at 200degree on a 60degree bed, without any support or brim. I often print 4 at a time.
I have added a second file, which has rounded corners. It prints with the same settings, and works just as well. The white dice at the back of the main image is one of the rounded corner prints.