What is IBM's biggest product?

I'm curious to know, what exactly do you consider to be IBM's biggest product? Is it their hardware like servers and computers, or is it their software offerings like Watson or Cloud services? Could it be their consulting and business services that cater to a wide range of industries? I'm eager to understand the criteria behind your answer, as IBM has a vast portfolio spanning across technology sectors. Please elaborate on what you perceive as their flagship product.