Is it possible for me to take Improved Critical:(improvised weapon)?

[IQuarent]

Title says it all.

Although I would extend that to weapon focus, etc.

[Strannik]

No. Those feats require you to be proficient in the weapon you choose, and everyone is assumed to be nonproficient w/ improvised weapons. Even Catch Off Guard only removes the penalties, not grant proficiency.

I'm unaware of any way to gain such proficiency. Perhaps someone else is aware of such an option?

[Xaratherus]

Within Pathfinder, I don't believe so. There was apparently a prestige class in one of the older Dragon magazines called Brawler that granted proficiency with improvised weapons but I don't see that it was ported over.

The closest I can find is the Low Templar PrC, which states that you don't take non-proficiency penalties with improvised weapons - but that still probably doesn't count as proficiency with them...

[ProggyBS]

A 9th level Fighter with the Cad archetype gets "Razor Sharp Chair leg" which aside from allowing you to alter the damage type of any improvised weapon, changes the critical threat rating to 19-20x2 with any improvised weapon.

That's about the closest you can get to increasing the threat range.

[IQuarent]

Well, the reason I asked was because of the monk of the empty hand arch type, which is about as close as it can get. Considering the fact that they get Catch Off-Guard and Improvised Weapon Mastery as bonus feats, as well as the ability to change damage types and add magical properties to improvised weapons.

[Strannik]

A friendly GM might house rule it for you (b/c monks are far from overpowered),allowing you to take those feats, but it doesn't look like this would fly in PFS. Not sure what kind of game you are in...