While i agree with Starglim i would love to actually love an archetype that did this and may houserule one thank you very much Ornery.
I'm guessing there is probably something in the rules that prohibits wearing a buckler on each elbow/forearm, but given the amount of newish shield feats that have been put into play recently, is it possible to work a brawler type melee character who uses said shield feats, gauntlets and gratuitous head butts?
Just spaghetti on the wall
Caveat: I've not read Ultimate Combat so I don't know if I'm missing a new rule.
Beyond the fact that RAW probably doesn't say you can't wear two shields because, with all due respect, they assumed most people have enough common sense to know you oughtn't wear two shields... two things you need to bear in mind.
1. There is no mechanical benefit to wearing two shields as Starglim noted--the bonuses will not stack (although the armor check penalty will for non masterwork bucklers)
2. Unless UC has something that changes this, you can't shield bash with a buckler (per the description under Equipment in the Core rules), if you were thinking of doing that (if you weren't then you're good on that).
Two thing you need to work out with your GM:
1. Gauntlet attacks are considered unarmed; spiked gauntlets considered armed (i.e., spiked gauntlets are considered a weapon). If you get spiked gauntlets, you need to work out whether the buckler attack penalty applies.
2. There is no clear ruling that unarmed strikes are only done with fists; however the monk class specifies that a monk can use an unarmed strike even with his hands full, suggesting non-monks ARE usually attacking only with their hands. I think it's perfectly sensible, mind, to allow a brawler to use head butts--but it IS something you'll want to get a clear ruling from your GM on.
I think a brawler with a buckler is a good idea, by the way! I just don't see the necessity or benefit to having two (think about how you would pay for upgrading them as you level up as well, if your GM let you have two).