Dual-wield light crossbows

But you can't dual-wield slings... And if you have +10 str mod, you probably shouldn't go ranged anyway (lower hit chance and possibly lack of useful feats). One can change (in protos.tab) weapon class from bow to sling - attack looks ridiculous, but full strength is utilized

 

New to me, I just discovered (by accident) that a sling can be used to make attacks of opportunity.