Easiest way to get around estate tax is to tie a big chunk of your money up in precious metals that aren't reported. Your beneficiaries know where the metals are after you die and can gradually sell it off, cash transactions, as they need money. The same is true for guns, art, collectible currency... Don't name it in your will and only let the beneficiary know how to get to it.
The same is true with cash.
I know someone in his 80s who randomly withdraws odd amounts in the $5-10k range and sticks it in a safe. When he dies and his friend opens the safe and finds $500k in there, he'll spend it and never pay a tax.