Mida Y1 D1. No TTK ornaments, no D2 redesign. No D2 ornaments. Just the original baby. My all time favorite gun in the game and I still use it daily to this day. Still the original skin is the best:
Tllaloc:
Touch of Malice:
Because I main a Titan and love being punished because of it I also love the look of Immobius:
and Fabian Strategy
Both were incredibly niche all things considered but I loved their looks. Very Titan-like. Utilitarian and no non-sense but effective.
There's a few others already mentioned here I won't repeat but I wanted to finish with another 2 favs:
Boolean Gemini:
I don't know exactly why I like it so much but it's just such a cool looking weapon. It wasn't very effective in PVP against other scouts and pusles but it was one of my favorite to look at. The other fav was:
Murmur:
I really enjoyed the sleek living machine look of the Hive stuff, Nechrocasm included. Plus this had the most satisfying sound of any weapon when it was fired and scored a kill. I really want it back in D2 but know it's probably a certainty we won't ever see it again.