Curious if they'll make another no weakness Pokemon again. Sableye and Spiritomb had the glory until Gen 6 when they got a Fairy weakness, and now only Eelektross(And it's pre evolutions) remains as being the only Pokemon without any weaknesses; albeit, only because of it's Ability(If it loses it then it's weak to Ground).
As it stands, it's impossible for any type combination to result in no weaknesses now, but like with Eelektross, there are current possibilities with the use of Abilities:
-Obviously, another Electric with Levitate, but rather something different.
-Water/Ground with Sap Sipper. Sap Sipper is "Herbivorous" in the Japanese games, as such, only really need a herbivore that lives on land and water, and the Marine Iguana seems like a great candidate. I have no issues with having another Lizard this Gen.
-Poison/Dark with Levitate. Just give it to Skuntank/Drapion. There are probably plenty Insects that could fit this, albeit, they'll have to not have the Bug type which would be a bit odd, but...Drapion. But to drive away from Drapion, how about a Jellyfish, albeit, again, odd not to have Water type but whatever. I would suggest the Portuguese man o' war over Jellyfish though(It looks like one but it's not), just for something different, but there are a lot of interesting Jellyfishes to use too. Non-Animal is probably a good choice for the typing too, or even some sort of mythical creature, nothing really comes to mind though.
-Bug/Steel with Flash Fire. Might be a difficult thing to think or make without putting in some personal touches. But there seems to be at least four Insects/Insect-like that could fit. Bombardier Beetle, being a Beetle it's easy enough to just give it armor to give it the Steel type, as for Flash Fire, it's more due to the fact they have a hot spray, so to put a personal touch, have some sort of filter that absorbs Fire attacks to power it up. Pompeii Worm, they have a bunch of Bacteria on them which looks like fur in a sense, and it's thought to provide insulation, so the Bacterial could be expanded on to be a armor of sort and allow it to have Steel type, and they can survive in very hot water so the Bacteria armor could serve as a means to absorb Fire attacks. There is also the Sahara Desert Ant, the Steel type is the tricky part but looking at Durant, it's possible to just give it armor too, it can survive the heat on land far better than anything else which can give it reason to have Flash Fire, also, they have to keep moving while in extreme heats or they will fry, so could be fun to see it as a Pokemon where it's constantly moving. And finally, Tardigrade, now the only thing with this one is that is can survive the extreme heat and cold; more than any other Animal, so seems better to give it an Ability that reflects on that(And other features about it that show it can survive in all sorts of different conditions). The Beetle I say works out the best since it uses a hot spray to attack already, but they all should be fine.
That's all the possibilities using the current Abilities. There's of course more possibilities if new Abilities come to grant new immunities in some form.