Before giving too many suggestions, it might be helpful to know what kind of guitar you've got, what pickups are in it, and what your current switching scheme is. (i.e. What kind of switch and which pickups/coils are activated in each position.)
To have the push/pull switch act as a dB boost, you'd need an active (battery-powered) preamp on-board.
You could use it to access a
pickup combo that isn't otherwise available on your guitar.
Another option is to have it act as a bypass or "blower" switch, where it connects your
bridge humbucker directly to the output jack, bypassing the pickup selector, the volume and the tone controls.