Safe (formerly Gnosis Safe) is a smart-contract multi-sig wallet that has become the de facto standard for treasury and admin keys on EVM chains. It supports a configurable threshold of signers, a transaction queue (proposers and signers can be different), modules for specialised behaviour, and fine-grained recovery configurations.
Safe transactions go through a queue: a signer proposes a transaction, other signers sign it off-chain, and any address can submit the bundle once the threshold is met. This separation between proposing and executing is operationally useful but introduces its own risks, a malicious proposal can sit in the queue and be approved by inattentive signers.
Safe is open-source, audited, and widely battle-tested. The vulnerabilities that hit Safe-based treasuries are almost never bugs in Safe itself, they're operational mistakes: signers signing transactions they didn't simulate, signers added without proper vetting, or the front-end being phished.