Destroyers: that was a drag down pain in the *** back in those days, and finally getting those made it feel like I had finally "made it".
Joyeuse: managed to coerce a monk friend into fighting the NM for me while I cured on RDM. I had managed to catch Charybdis up after maintenance, so he hurried over and we duoed him, with someone standing and waiting to steal if we wiped.
Byakkos Haidate: because DKP systems are terrible.
Ochiudo's Kote: I killed so many tigers to make money for these. so. many. dead. tigers.
Black Belt: cost me a million each for Tongue/Whisker, and got the egg myself. I do not lament the death of HNM botting one bit.
Spharai: the PAIN knuckles were always a long time goal.
Gungnir: it was such a laughable weapon for such a long time, but it was my first Relic way back when BSTs ruled Dynamis. PUP WS proc window ftw.
I am sure I could find a dozen things just sitting in Storage, but these all immediately spring to mind.