There are a whole class of assets that pass without the need for probate, if you've properly named beneficiaries on those accounts. These include life insurance policies, pay-on-death accounts, and retirement plans (e.g., IRAs, 401ks, etc.).
If you acquired any of these assets during marriage, and absent an agreement between you and your spouse to the contrary, each spouse should have a 1/2 interest in each since they would be considered community property. Therefore, even if you've been funding your 401k plan at work with your salary, because that salary is considered community property, your spouse has a 1/2 interest in the account.
Because the law recognizes the community property nature of these assets, if you want to name a beneficiary for your 401k (other than your spouse), your spouse must consent and typically must also sign the beneficiary designation form waiving his or her right.
Check out California Probate Code Section 5020, which states:
"A provision for a nonprobate transfer of community property on death executed by a married person without the written consent of the person’s spouse (1) is not effective as to the nonconsenting spouse’s interest in the property and (2) does not affect the nonconsenting spouse’s disposition on death of the nonconsenting spouse’s interest in the community property by will, intestate succession, or nonprobate transfer."
If you're like many clients, you have probably never checked on the beneficiary designations on assets such as life insurance policies or retirement accounts since you acquired them. You might have acquired some of those accounts before you got married and named your parents or a sibling as the beneficiary.
Part of the estate planning process should entail you reviewing assets which are transferred by beneficiary designation to make sure they are up to date.