Social Security Benefits
If either you or your spouse don't qualify for your own Social Security benefits, you can receive the other spouse's benefits. The payoff isn't immediate, though -- you have to either be at least 62 years old or be any age but caring for a child who can receive benefits and is younger than 16 years old or disabled. You can also potentially receive Medicare, disability, veterans, military and pension plan benefits through your spouse.
(And although this is a bit of a buzzkill statement, knowledge is power. If your marriage ends but lasted at least 10 years, you may still be able to receive Social Security benefits on your former spouse's record. Aside from that, you'd also have entitlement to spousal support.)