If you mean when giving types to a pokemon, I'd say Rock and Ice (sorry Aurorus, I still love you, but your type is as horrible as Leavanny's. I also love you, Leavanny, but your type...)
The only thing you can combine these two to get a somewhat decent typing leaves them with still plenty of weaknesses and few or no resistances at all.
Ice makes a good combo with either Water or Electric (the only non pure ice type combos that have four weaknesses with none of them being a x4 times weakness; also, NO type combo with ice can possibly have less than 4 weaknesses naturally, that's how bad of a defensive type it is). In my opinion, Ice could really benefit from some resistances: Grass, Flying and Ground, for example (and if you stretch it enough, maybe even Water, since ice floats over it, and Dragon, because some lizards die in the cold...generally), could make it a lot more viable when they're the type of a pokemon, and not just the type of the moves, because I'll admit that as an attacking type, Ice is pretty good.
As for Rock, the most decent defensive combo is when paired with Grass (ironic that the two types with the most weaknesses cancel most of each other's down) and also Flying. In my opinion rock should resist more things: itself, to begin with, and also Bug and Ice, to say the least. Other good resistances, even though a bit farfetched, could be against Dark and Electric. Just like Ice, rock is pretty good offensively, but I don't think giving it five weaknesses is justified just for that.
And offensively, well I think every type has its strengths at some point, in some battle, somewhere. Specially when they receive STAB from the pokemon using the moves. If I had to say one, um, well Steel is pretty terrible outside of Iron head and Meteor Mash/Bullet Punch. All not-so-powerful moves with bad accuracy and that are generally only useful against fairies. A close second would be Ghost, if it wasn't so good to deal with Mega Gardevoir & Gallade. But anyways ghost is more to annoy and burn people than to attack them directly. Poison types aren't as bad as you think, neither offensively or defensively.
It also took me like three minutes to choose a color for every type mentioned, so I don't even know why I bother. It's pretty tho
EDIT: I didn't put grass together with ice and rock because at least grass, while not that good as attacking type (not even against water types generally, only good when thunderbolt can't do its job against water/ground bulkers...), is at least somewhat decent if paired in a good type combo. For instance, Grass/steel has only two weaknesses, and yeah despite one of them being a 4x kind, you just have to make sure there are no fire benders in the field before switching into it. The classic grass/poison is as well pretty decent, and the same for grass/water and grass/fire... if this last one actually existed, that is.