I think we've all gone onto Wonder Trade and received a Pokemon that was just... super disappointing. Like an extremely common, beginning-of-the-game, low level Pokemon. I thought here, we could write down what Pokemon we think are best to go into the Wonder Trade so we can encourage fair Wonder Trades!
I'm not the most knowledgeable person in the world on Pokemon values, but I think version exclusives and trade-to-evolve Pokemon are great to Wonder Trade!
Also, include the version of the game you are talking about, as a Pokemon that might be super plentiful in one game might be pretty rare in another!
Stuff I prefer to see: Breedjects, HAs, egg moves, and breedable Pokemon that you can't catch in Sun/Moon.
I see the first 3 more than I see the latter. As someone who completely skipped gen 6 (X/Y, Omega Ruby/Alpha Sapphire), there's breedable stuff I'd love to receive from Wonder Trade. I'm sure I'm not alone.
as many others have said, decent breedjects and game/region exclusives are always good, especially if it's a Pokemon you can't usually get in the game you're trading it in (I.e. poketransferred mons, etc)
I think vivillions are great, too! lots of people want to complete their collections of different patterns, and they're especially good if you live somewhere uncommon or where you don't usually see other players come from. c:
I usually just trade breedjects, but yesterday I was lucky and traded for a few non Alolan form Kanto Pok?mon on gts. Maybe I'll breed some Kanto Meowth, Ratatta, and Vulpix and pass on the fun.
Haven't really done a serious amount of wondertrading in sun/moon until this evening, and I'm releasing all the chansey from egg hatching (no results aaa) and I'm surprised, there's almost nothing crappy (like, not a single pikipek yet and only two yungoos), and some are really impressive, like rareballs with nice species, evolved pokemon, evolved starters and even a shiny (which I'm not a fool to think would be 100% legit, but which I like to imagine could just be a clone, either way, interesting and exciting and not at all repetitive results!
As for whether people are happy to receive my premier ball chansey, not sure!
I haven't utilized Wonder Trade in a while, but whenever I used it in the past I would tend to trade away things with good natures, 5 or 6 IVs, sometimes egg moves, whatever their best Abilities were, and Pokerus. These would be Pokemon that I was either breeding for a team I was building or that had some relation to the time period (like, say, Pumpkaboo for Halloween, Delibird or Snover for Christmas, etc.) at the time I was conducting the Wonder Trades.