1. If your spouse dies, you may be eligible for survivors benefits under Social Security. In addition, the surviving spouse may have the choice of taking their own social security benefit or getting a percentage of their deceased spouse's benefit
2. If your spouse dies, you may be able to roll-over their IRA or 401(k) to your account with reduced or no tax penalties.
If you are a spouse, the rules for an IRA are pretty lenient - you can roll over the IRA into your own, and then defer paying taxes on it until you decide to withdraw from the account. But you still have to pay taxes on it, of course, when you withdraw the money from the plan.
If you decide to cash it in, however, it is considered ordinary income. And if you are cashing in a $250,000 account, that will likely push you in to a much higher income bracket, and you will be expected to pay State and Federal taxes on this. And to prevent unpleasant surprises on April 15th, you need to mail in some estimated tax payments ahead of time.
UPDATE: My Big Fat Gay Wedding, Provincetown, Mass, July 2014: