I literally hit two today. Off the top of my head:

    def enhance_payload(payload)
      payload[:h] = thing_h

      if situation_one?
        payload[:a] = thing_a
        payload[:b] = thing_b
      end

      if situation_two?
        payload[:x] = thing_x
        payload[:y] = thing_y
      end
    end

Which RuboCop suggests to turn into:

    def enhance_payload(payload)
      payload[:h] = thing_h

      if situation_one?
        payload[:a] = thing_a
        payload[:b] = thing_b
      end

      return unless situation_two?

      payload[:x] = thing_x
      payload[:y] = thing_y
    end

But if you move the first line of the method down to the be the last line, suddenly it's not important to use a guard clause anymore.

If you can't think of examples, then you haven't been doing much thinking.