Nice topic! Before 2021, I would never have thought I’d have a favorite arachnid, much less a list of them, but thanks to iNaturalist, I do. Like @Thunderhead’s, my arachnophobia is also easing as I seek out observations and strive for better photos of what I see. The variety of colors, patterns and even expressions you can see when you zoom in is amazing. I currently have 586 observations of 126 species of arachnid (good job, self!). Some of my favorites are:
Of the 3 times I’ve seen pseudoscorpions, 2 were examples of phoresy 
Salticidae (Jumping spiders)
These spiders can have beautiful colors, like the shiny pink above, and even blue as shown recently in the blue organisms thread (WOW!). They strike funny poses, seem to wave a friendly hello, and assume adorable pensive expressions. One of the most interesting things I got to see was when 2 males had a battle. I didn’t stay to see the end result, I wasn’t ready to witness what might happen, but I got a series showing the match.
I also really like the Micrathena spiders.
Micrathenas are very tiny, and are hard to get the camera to focus on (at least for me), but when you manage it (try using a mirror, it helps!), you get to see their crazy shape, beautiful patterning, and their lovely web structure! 
(Edit: the right-most picture of the Micrathena gracilis I got by holding a mirror under the spider and taking a picture of the reflection, since I was unwilling to try to crawl under and look up. (-: )