What's your Favorite Compression items?
Could be Element or Type swapping, Tome with multiple spells, Morphing item that grants armor (Frogzard Sword, Shapeshifter Forms, Omega Astramorph, etc), Multi-Guests (Class/Subrace armor), or even just something with a multitude of effects (Legendary Shadow Crystal, QuadMod, Terror Visage, etc.)
My favorite is Golem Summoner Robes. Not the best armor or guests (big penalties for having all standard 8 elements) but golems are a cool monster species.
The Wind Stone misc gets a honorable mention. Actually "decompression" (need a Pet + Guest) and the Sleep effect is now replicated easier by Woolzard but nonetheless the evolution mechanic is cool.
I also hope something like Conjure Shadow spell or Wizards of Waverly Place collab weapons are released again one day. Weapon/Armor/Guest compression is so cool.