Or fireworks. Many states have laws against selling fireworks to state residents, but all you need to do is cross a border or have an out of state license and you can buy them just fine.

I thought there was a relatively good explanation for ice spikes having to do with the volumetric expansion of water as it transitions phases from liquid to solid. Basically as an ice cube freezes there is a shell formed over the top surface and under the right circumstances it forms from the outside edges in leaving a hole, but then instead of the hole closing over ice starts forming downward into the bulk of the cube, pushing liquid water out of the hole which is then frozen into a protrusion

https://en.m.wikipedia.org/wiki/Ice_spike

I knew one day this time would come.