he and singed, though singed atleast has the melee ranged fling and mostly just runs around for damage, useing any AAs generally is wierd on singed as he's best off running close to his opponents, but just out of range. And he once had a strong AA steroid on his ult.
Zac also has no AA synergie, but like singed, he needs to walk around alot in fights to get his passive blobs, so stopping for AAs doesn't fit that well. Also, his Q feels a bit like a AA and his W rewards him for sticking in close range, which also means he can easily sneak in AAs every now and then so he still feels quite meele
There are also some other with no AA stuff in their kit, which theirfor scale off ad and thus profit alot from AAing.
And there is Kata, though she kinda automatically AAs after E, and she generally needs to go in meleerange to do stuff, so it doesn't feel wierd.
On Gallio, the melee AAs just feel wierd, outside of his ult every now and then, he has ZERO reason to ever go in melee range. It's imo a big part of why gallio feels a bit off and has such a low playerbase. For me, he would be alot more fun to use if my AAs actually did something, so i get more rewarded for getting close AS A TANK/OFF-TANK.