gistfile1.rb

#!/usr/bin/env ruby
# coding: utf-8

hash = [
  {hoge: {fuga: 3}},
  {hoge: {homu: 5}},
  {fuga: {hoge: 4}},
  {fuga: {pero: 6}}
]
 
hash1 = hash.group_by{|h| h.keys}
           .map{|k,arr|
             {k.first => arr.map{|a| a.values}.flatten.inject(:merge)}
           }.inject(:merge)
 
p hash1
#=> {:hoge=>{:fuga=>3, :homu=>5}, :fuga=>{:hoge=>4, :pero=>6}}

require "active_support/core_ext"
 
p hash.inject({}){|ha, h| ha.deep_merge(h)}
#=> {:hoge=>{:fuga=>3, :homu=>5}, :fuga=>{:hoge=>4, :pero=>6}}