"No one, and I mean no one has a phased polaron cannon!"
"I do. In my weapons archive."
A Phased polaron cannon is a blocky-looking silver weapon capable of shooting a high-intensity laser beam vast distances (into space and as far away as nearby black holes). The only extant phased polaron cannon was designed by Niels Bohr, and is in the custody of The Middleman, kept in the Weapons Archive at Middleman Headquarters. Bohr seems to have a good relationship with the organization, and is on Christmas card terms with the present Middleman.
If two phased polaron cannons in separate (but mirror) universes are fired through the same black hole from the same point at the exact same time, the collision will create a Quantum singularity, a bridge between the two worlds. The effects of this can be duplicated with a Quantum Singularity Machine.
Said prop later showed up in Dr. Horrible's SingAlong Blog as Dr. Horrible's Freeze Ray.