I really enjoy the fossil Pokémon, particularly those based on marine creatures. I even had my mom make me a Kabuto plush when I was younger. I also really enjoyed digging for fossils in DPPt and really hope they bring that feature back in future games (not just DP remakes).
My favorite fossil Pokémon is Omanyte, but not because those annoying Twitch references. I like it mainly because I remember trading half of my snack one day for a Japanese Omanyte card way back in elementary school and thought the art was
adorable, and it was one of the first Pokémon with not-so-obvious origins that I connected to the real world thanks to a book about fossils in the school library. (To this day, I still know people who think it's a snail.)
After discovering fossils on my family's property a few years ago, I most wanted to find an ammonite (the spiral-shelled squids that inspired Omanyte). Things weren't looking up since I was mainly finding terrestrial plant fossils, but one day I stumbled upon an ammonoid fossil in the creek rubble! A bit small and worn but, hey, real-life Helix Fossil! (Note: This ammonoid is a goniatite, not a
true ammonite. It's related though, and some still define it as a small type of ammonite, so close enough for me!)
I even SR'd a Shiny Omanyte earlier this year. :D