The HSA, quietly the best account there is
What it is: a Health Savings Account, available if you have a qualifying high-deductible health plan.
Why it is unusual: it is the only account taxed at *none* of the three stages. Money goes in pre-tax, grows untaxed, and comes out untaxed when spent on qualifying medical costs. A 401(k) taxes the exit. A Roth taxes the entry. An HSA taxes neither.
The move most people miss: you do not have to spend it now. Pay medical costs from cash, keep the receipts, invest the HSA, and reimburse yourself decades later. There is generally no deadline on that reimbursement.
The catch: you need the right health plan to contribute, and non-medical withdrawals before 65 are taxed and penalised.
Chart: where each account takes its cut.