The Fabfilter creative plugins (Timeless, Saturn, Volcano) have a real wow factor that made me buy them.  After a few months I sold them though. For me, there are just way too many options, and I drown in a sea of choice and endless tweaking.

I use Pro-L all of the time. I love how their plugins are so visual. I feel like I have a really good idea of how I'm effecting my signal when I use Pro-L or Pro-Q 2. I also use Simplon a lot as opposed to something like autofilter in Ableton solely because I like how it looks lol

I'm a fab filter whore! I cannot champion Fabfilter enough. I use practically all their plugins, the only one I don't have but want to buy is the Pro-MB.

The versatility, functionality and user interfaces of all their plugins are amazing. I really like the pro-q2 because of the sharp Q curves you can achieve, The mid-side EQ on it is great and there is also a feature where you can freeze the analyser and it will show any peaks - you can then highlight the waveform of the analyser and pull the specific peaks down- really handy. I also like the fact you can solo a frequency band - so I like to create large and narrow boosts then solo the frequency band hunt out any problematic frequencies!

The fab filter plugins are boss!!  I use their compressor, timeless and volcano a lot also!  And their Saturn plugin is probably in every single one of my projects also.