What kind of Bitcoin transactions or protocols make use of transaction scripts that involve operations beyond simply validating signatures or multi-signatures?
Transactions like the Lightning Network force-close channel transactions, which use hashes and time locks.
Several active protocols depend on non-signature opcodes. The Lightning Network uses hash conditions and timelocks in HTLCs, which require either revealing a preimage or waiting out a timeout to claim funds. Vault designs rely on timelocks like OP_CHECKLOCKTIMEVERIFY and OP_CHECKSEQUENCEVERIFY to create delayed spending and recovery paths. Discreet Log Contracts combine signatures with hash and timelock checks to enforce payouts linked to external events. On the research side, covenant constructions and experiments like ColliderScript show how non-signature logic can be used to restrict future spends without new opcodes.