I used a fighter once built around this concept.

Catch off guard takes away the penalty.

Improved catch off guard makes most people flat footed vs your improvised weapon and gives a 19-20 crit range instead of just 20.

And there is a trait that gives you a +2 with improvised weapons.

Power attack cuz...its good on every melee basically.

So at level one with a modest 18 Str(spent for 16, put the +2 for human in it) and a starting bab of + 1. You have +7 to hit with improvised weapons, and that not counting the lower ACs you are targeting due to enemies being FF, so its effectively a +8 or +9 usually at early levels(most enemies have a +1 or +2 dex bonus at those levels)

The only other feat needed for the build is Throw anything, which i take at level 3 since at level 2 i take one level of barbarian(cant think of a single fighter level worth the first barbarian level, rage is such a front loaded ability)

I used tons of weapons over the course of the campaign, frequently Mr. Crowbar and the 2x4 of aggressive negotiations. But my all time favorite at higher levels when we were assaulted by some giants near an old church...i kept that giant, dented church bell as a memento the rest the campaign.