Roth IRA

A Roth IRA flips the traditional deal: you pay tax now, and never again. Contributions aren't deductible, but withdrawals in retirement — including decades of growth — are completely tax-free. Young earners in lower brackets today tend to love it, since they're prepaying tax at a discount.

Example: Contribute $7,500 at 25, let it compound at 7% to about $112,000 by 65, and withdraw every penny tax-free.