Should a California move-out checklist be signed?

Yes. A signed move-in and matching signed move-out checklist is the single strongest evidence in a California deposit dispute. The tenant's signature at move-in agreeing the unit was in good condition, combined with a signed move-out report documenting any changes, gives the landlord a clear documentary record. Without signatures, the tenant can argue the damage existed at move-in, and in a he-said-she-said dispute, courts often favor the tenant. Every room, appliance, floor, wall, and fixture should be noted with condition.

Source: California evidentiary practice