That is a tough one, I have had a lot of luck with wondertrade, a Shiny Staraptor here, a Rayquazza there. One of my best was probably a shiny genesect or hmmmm I really dont know, I have gotten a lot of Pokémon I loved from wonder trade that are very good or rare. I could just list out the shiny Pokémon I have gotten, same with legendary Pokémon.
It's a tossup between Shiny 5IV Adamant Crobat and this German shiny 5iv Adamant Braviary . Honorable mention goes to an awesome person who once traded me a great Onix that evolved into a Steelix, my favorite Pokémon as a kid. I try to give out good ones in return and trade evolutions like Rock Smash-encounter Gravellers and Porygons into Porygon2 cause I know what it's like to need a trade evo and not have trusted people trade with, and have given away extra shinies before, gotta keep Wonder Trade good. I typically go through cycles whee I have half a box to a box of WT Pokémon and alternate days, one day for Gen 1-3, the next for 4-6, and just trade until I have no more of any of those Pokémon left in the box, repeats, or get garbage Pokémon which get released and become holes. So it's like a game to see if you can maintain the box size over time based on how many garbage Pokémon you get. Once in a while something awesome comes and I take that for myself, but rarely. A huge plus to this is that I have at least a free PP UP every day in Lilycove, and frequently PP Max which I like as gifts for giveaways and trades. I Wonder Trade a lot, out of the 177 current hours on Omega Ruby probably a good 30 total of it was WT. I find it fun and I try to cleanse the Wonder Trade system by releasing specific garbage Pokémon I receive instead of sending them back out, for example these days Wurmple, Zigzagoon and Poochyena. I implore you to do the same! Keep the Zigzagoon population down, release those garbage trades! It's like Bob Barker with his spay and neuter your pets thing, Do Your Part To Maintain WT Quality I hope they don't change anything about WT in Sun and Moon, it's perfect as it is.
I think that it might be my shiny LV 99 Dragonair. She was a real gem and the previous owner was kind enough to allow me the decision to evolve her to a Dragonite is I so wish. (I don't.)
I got a LV70 Heliolisk and a LV69 Flygon out of the Wonder Trade! They're not shiny and tgeir IVs are nothing special, but I still found it to be pretty special to have gotten two Pokémon I would never use, who are already relatively strong and might have had another loving Trainer before they got to me who had to trade them away because of a Wonderlocke or whatever, so I decided to keep them around and train them even further. Now they're two of my most trusted partners <3
