Urgh, I can't pick a favorite. I'll just rate them. Green is good, red is bad, etc.
Royal Gel - Definitely one of my favorites. I enjoy being able to walk through slimes with impunity.
Shield of Cthulhu - It's fantastic for impromptu dodging. Being able to ram into enemies at the same time makes it even more useful than the Black Belt, perhaps.
0x33's Aviators - This was a thing?
I honestly had no idea. Isn't it just a vanity thing?
Worm Scarf - A nice 17% reduction in damage taken, but I'd rather just not touch an enemy at all.
Bone Glove - I never use throwing weapons. I also like to save all of my bones for building things or recipes.
Hive Pack - It's nice when you have bees, sure. Bees are often seen as an overlooked strategic offense in Terraria, but they can really pack a punch.
Demon Heart - Absolutely. I love having more accessories.
Mechanical Minecart - I love speed, but I mostly set up a series of teleports around the world anyway. By the time I get this, we should already have the Steampunker and access to her teleporters.
Spore Sac - I have really bad luck with this. Nothing ever seems to come into contact with the spores, so it's a bit useless for me.
Shiny Stone - Enhanced regeneration is nice, but there are accessories I'd rather have that will help keep me out of danger entirely.
Shrimpy Truffle - I tend to go for the Cosmic Car Key anyway.
Gravity Globe - If I already have the Cosmic Car Key, why would I need this?
Suspicious Looking Tentacle - It's nice having a permanent bunch of buffs on, sure. I never use pets anyway.