Belt of holding.
the only magic tool Bruce has ever or will ever willingly use is his belt, he had Zatanna charm it with endless space in the pockets and swore her to secrecy. he refuses to admit this to anyone no matter what absurdity he pulls out of his belt, his kids are convinced something is up with it but they never caught him in the act or have managed to stick their hands in there yet, Bruce will stare people straight in the eye and pull an entire parachute out of a 3 square inch pocket and claim with outmost seriousness it was just folded up really tight,
when Dick takes over the cowl when Bruce is in the time stream and first gets his hands on the belt the sheer vindication overpowers the grief for a solid hour