New shotgun slug design, machined from copper. Very interesting, and very spendy.
Tam had something on this dry-fire practice setup not long ago. At $350 it's not inexpensive, but man, that would be wonderful for practice at home.
If you've though about the matter of literally burying a gun, here's some help. A guy found the story I've mentioned once before: guy buried a Mini-14 for 15 years. Still works fine.