Rails’ ActiveSupport library also gives you slice and except for dealing with the hash on a key level:
y = x.slice("one", "two") # => { "one" => "one", "two" => "two" }
y = x.except("three") # => { "one" => "one", "two" => "two" }
x.slice!("one", "two") # x is now { "one" => "one", "two" => "two" }
These are quite nice, and I use them all the time.