Rigby↑
When did Apple last use a proprietary connector on Macs? I can't think of a single one (except for the power connector, where until recently no standard existed).
ADB, used for keyboards prior to the introduction of USB, though the physical connector itself complied with an industry standard. Before that, Apple's video connector and serial port connectors were semi-proprietary. (The physical connector complied with a standard, and the serial port's signaling complied with a standard; it just wasn't the connector or the standard used by the rest of the industry.) But basically, nothing built in this century unless you count internal connectors.