ZoneAlarm, Neoplanet, Viruscan, etc...
...Spotify, Chrome, Firefox, Office. Newer applications are less obvious offenders, but rendering custom UI controls (often to emulate the look of a specific setup) instead of just using the OS defaults is still a surprisingly common practice. Spotify, Firefox, and Office are particularly bad offenders, since Spotify blatantly emulates whatever Windows is the most recent, Firefox looks, feels, and acts like it was written for Mac OS, and Office takes on whatever graphical form was popular at the time... forever.
Edit: I just remembered that AMD's Ryzen overclocking utility and Radeon settings applications are also clearly skinned for Windows 10. How dated are they going to look 10 years down the line?
Dual Katmai Pentium III (450 and 600MHz), 512ish MB RAM, 40 GB HDD, ATI Rage 128 | K6-2 400MHz / Pentium MMX 166, 80MB RAM, ~2GB Quantum Bigfoot, Awful integrated S3 graphics.