One of the most common grammatical mistakes that I see among younger folk these days is the word stuff with an additional, and quite unecessary, “s” at the end. I suppose this is an attempt to show the plural form of the noun, where we usually add an “s” at the end to indicate having more than one. For example, “I got a bunch of stuffs from my relative in the States, including two St. Moritz watches.
What some people do not realize is that the word “stuff” is a mass noun, also known as an uncountable noun. Mass nouns have no plural form because they connote a collection of items that cannot be measured. All the stuff on your desk, for example, is the correct usage, not “stuffs on your desk.”
Whenever I see the word “stuffs” in reference to a collection if items, I feel like stuffing the speaker/writer into a sack and hanging it from a tree. 😛