Left handed trackball (Elecom). Sits to the left of my Moonlander while my vertical mouse sits to the right. Not only is it convenient, as an old school Diablo player I get to tell people I duel wield.
I also have a cheap X-Pen graphics tablet that I use for ‘white boarding’ on zoom calls.
Almost forgot I also have a usb wireless numpad that I pair with a usb hid remapped on a pi zero to make hot keys for frequent actions.
I have an XP-Pen as well. Works great in Linux. I'm still amazed at how high quality these non-Wacom tablets are today. I had one of those cheap 6" Wacom Graphites back in the early 2000s and that was the best you could get. My XP-Pen blows that thing away. Still haven't found a great place to put it though. I'm just stashing it off to the side but it's awkward moving it around all the time.
When I travel I wind up working in all sorts of odd setups. No need to find a flat place to move a mouse. It works in tight places and uneven surfaces such as a couch.
+1 on the left-handed trackball and right-handed vertical mouse. I don't use both together, though. My trackball is a Kensington Orbit, with scroll ring.
I also have a cheap graphics tables, a Huion, for some digital painting or to help with creating software architecture diagrams.
+1 on graphics tablet. I got a Huion HS611. Surprisingly cheap and it becomes much easier to draw diagrams, annotate images, sign signatures, etc with your hand instead of a mouse. Highly recommended for those who need to draw, make diagrams etc.
I also have a cheap X-Pen graphics tablet that I use for ‘white boarding’ on zoom calls.
Almost forgot I also have a usb wireless numpad that I pair with a usb hid remapped on a pi zero to make hot keys for frequent actions.