answers will be given for Played Against/Used
Great Brass Scorpion - No/No
Astraeus Super-Heavy Tank - No/No
Ork Gargantuan Squiggoth - No/Yes - I own one & it comes out to play on occasion
Ork "Chinork" Warcopta - No/Yes - I have 1 scratch built
Scorpion Type II Heavy Grav Tank - No/Yes - though technically mine is an old Armourcast Tempest
XV108 Y'vahra Battlesuit - Yes/No
KX139 Ta'unar Supremacy Armour - Yes/No
Tyranid Harridan - No/Yes - Love my Tyranid dragon!

And honestly it's served as a D&D dragon far more often than it's seen
40k play
Legio Custodes Ares Gunship - Yes, fairly often/No
Mastodon Super-Heavy Assault Transport - No/No - but it is on the to do list.
Acastus Knight Porphyrion - Yes/No
Eldar Phantom Titan - Yes, looong ago/Yes, loong ago - mine is the old Armorcast model
Mechanicum Ordinatus Ulator - No/No
Mechanicum Krios Battle Tank - In Horus Heresy yes, in
40k no/No
Dark Eldar Tantalus - No/No
Chaplain Venerable Dreadnought - Yes/Yes
Mars Pattern Warhound Titan - Yes/Yes - I have several Armorcast & 1
FW
Thunderhawk Gunship - No/Yes - though mine is the
LE all metal one from before
FW was a thing
Mars Pattern Reaver Titan - Yes/Yes - Mine are all Armorcast
Legion Sokar Stormbird - Yes/No
Arvus Lighter - No/No
Mars-Alpha Pattern Volcano Cannon Warbringer Nemesis Titan - No/No
Mars Pattern Warlord Titan - Yes/No
Tau Manta - No/No
Necron Pylon - No/Yes
Imperial Navy Marauder Bomber - No/Yes
I've also used a great many other things found on the Legends lists, be they
FW pieces or otherwise.
In fact I make it a point to do so to A) show people that these things exist, B) because wether or not
GW still sells them,
I'm not done playing with my toys.