This was inspired by a trick mug shown on an episode of (The UK comic quiz show) QI.
The challenge is to drink water from the mug without any spillage. For those that know that the handle is hollow and open at the bottom end inside the mug, and that the band around the top of the mug is also hollow and that hollow connects to the hollow in the handle, then it is easy.
However those who haven't seen it before, and perhaps are put under a bit of time pressure....
I made two so that two people can compete.
Make in DiamondAge PLA on an Ultimaker 1.