3 solutions i can think of
1 - Mechanical. Make a lot more use of DR / Slashing, Piercing, Bludgeoning to encourage variation. Some of the weirder weapons might get around this (eg the bec-de-corbin was a right angled spike on a pole-arm designed to penetrate armours so would ignore DR/Bludgeoning)
2 - Flavour
Make weapons culturally significant. If 'everyone' knows that long-swords are used by the Evil Empire of the north, then just wearing one in public would give you a serious problem in social circumstances (unless you have a long story about killing an enemy leader). Equally a Halberd might be only issued to army veterans and so would grant you instant respect - (unless you're a foreigner and so must have gained it from looting the battlefield). Rapier would instantly identify you as a soft southern city dweller, bastard swords would instantly make you a feared tuscan raider, Scimitars are only used by nobles in the service of the king, war hammers are used by revolting peasants...
You can even make it vary locally (in one city-state all cross bows are banned after the death of the Princes son in a sporting accident).
And also apply it to races - Dwarves will look with suspicion on any of their kind not using an axe since the last great war of independence granted them the right to wear one in the human lands without hindrance, Elves without bows are treated with contempt in the elven forests. ("what are you, some kind of Half-Elf?") Every halfling clan has its own dagger type (variations on punching, normal & kukri) with different designs that instantly identify your origins to another halfling.
Of course, this means that magic items will be created based on this list, so expect to find lots of magic rapiers in the cities, magic halberds presented to heroic soldiers, etc etc with non-regional weapons being in very short supply (and possibly not even being made except where common so you can't even create your own magic item)
You could do the same thing with armour as well, to try and encourage a bit of variety in some of the medium armours. (you could use that as a bit of balancing as well - "yes, everyone knows that the great-axe is used by Veltan tribesmen, but they only use breastplates because plate is for wimps!")
10 minutes with a photocopy of the equipment list and a marker should sort it out, but make sure the players get a copy when creating characters or they'll be a bit annoyed they've spent three feats on using a lasso, that instantly identifies them as a sand-pirate....
Oh, and make sure you give a few choices to each region, even if one is stereotypical, so you don't end up with too many clones
3 - Setting
If you mix and match City / wilderness adventures then make Med / Heavy armour, shields & two-handed weapons prohibited in a city. Ensures even the tanks have a back up plan.