My (least) favorite example is that Microsoft got at least 3 patents out of Exfat in the late 2000s for trivial extensions of FAT32, which incorporated long-public, in-no-way-novel techniques to FAT in basically the most obvious possible way to add the features. (Basically: hashed directory entries for speed of lookup; a single extent design that only works for 100% contiguous files; and a free bitmap.) These things were easily predated by the same techniques in, e.g., ext3 (2001) and classic Berkeley FFS from the 80s, but MSFT gets to prevent unlicensed 3rd party ExFAT implementations until 2029, if not further.