Been thinking about Decidueye's movepool. While I'm certain it'll get the generic Ghost and Grass attacks that it should get (Seed Bomb, Leaf Blade, Shadow Claw, Phantom Force, maybe Shadow Sneak), the archer gimmick is interesting. There aren't any previous archer Pokemon, so I was trying to think of what possible coverage this unique gimmick could give it. Here are some thoughts, only looking at physical moves:
Ground:
Thousand Arrows - Unlikely given it's Zygarde's, but is is the only attack with "Arrow" in it's name.
Drill Run - Potentially a spinning arrow could provide the same sort of attack that spinning horns provide for other Pokemon with this attack.
Poison:
Gunk Shot - "Shot" being the operative word, appears in both English and Japanese version of the name (Dust Shoot in Japanese). Poison-tipped arrows are also a common trope.
Rock:
Rock Blast, Rock Throw, Rock Slide - all the same reason, perhaps a stone arrowhead. Calls to mind slings, which are similar ranged weapons.
Smack Down - What better way to ground a bird than shooting an arrow at it?
Bug:
Pin Missile - Has Missile in the name, easily translates to an arrow attack.
There's a few others that you could make arguments for but I consider significantly less likely (Icicle Spear, Ice Shard) and a few I consider fairly likely but they're not good (Spike Cannon). And there's a few notable moves that it will likely get that are independent of the archer gimmick (U-Turn for example, since most birds get it).
One notable thing I've realized is a lot of multihit moves make sense for an archery gimmick. Skill Link could be a good choice for Hidden Ability, and combine well with Bullet Seed. Don't see it as particularly likely though.