Through some extensive research I have concluded that no viable Pokemon can do all these things.
I begun by narrowing it down to all Pokemon that learn Taunt (full list can be found here) as that was the only solid move requirement. Now I choose to disregard the no-Spored trait and the Levitater/Flyer trait as those can be solved with items, Safety Googles and Air Balloon respectively. That, I felt, gave me a reasonable amount of Pokemon to work with. The great issue is the required type coverage, as Dark or Normal is needed to deal with Gengar effectively, Grass or Safety Googles are needed for Spore, Fire/Water/Ice/Steel to deal with Icy Wind and Flying/Levitate/Air Balloon are needed. As we can see, at least three types or two items to stop all four threats, something that is impossible.
As such, here is my list of things that fulfill as many of these requirements as possible without compromising viability. + will mean the Pokemon have the trait, - will mean it do not, +?- will mean it may or may not have the trait dependent on the set or isn't a perfect match.
Bisharp @ Air Balloon/Safety Googles
Ability: Defiant
EVs: 248 HP / 252 Atk / 8 SpD
Adamant Nature
- Iron Head
- Taunt
- Knock Off
- Thunder Wave
- Icy Wind
- Fairies
- Gengar
- Taunt
+?- Airborne
+?- Spore
Gallade @ Air Balloon
Ability: Justified
EVs: 248 HP / 252 Atk / 8 SpD
Adamant Nature
- Poison Jab
- Fire Punch
- Leaf Blade
- Knock Off
- Taunt
- Fire move
- Fairies
- Grass move
+?- Gengar
+?- Airborne
+?- Spore
-Icy Wind
Hydreigon @ Safety Goggles
Ability: Levitate
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Fire Blast
- Dark Pulse
- Hidden Power [Grass]/Taunt
- Flash Cannon
- Spore
- Fire move
- Gengar
- Airborne
+?- Fairies
+?- Grass move
+?-Taunt
Honchkrow @ Safety Goggles
Ability: Insomnia
EVs: 248 HP / 252 SpA / 8 SpD
Modest Nature
- Heat Wave
- Dark Pulse
- Taunt
- Hidden Power [Grass]
- Spore
- Fire move
- Grass move
- Gengar
- Airborne
- Taunt
Yveltal @ Safety Goggles
Ability: Dark Aura
EVs: 252 SpA / 4 SpD / 252 Spe
Timid Nature
- Heat Wave
- Hidden Power [Grass] [Steel]
- Dark Pulse
- Taunt
- Spore
- Fire move
- Gengar
- Airborne
- Taunt
+?- Grass
-?+ Fairies
Final thoughts: None of these sets are completely optmal, but by these requirements there is no optimal Pokemon. Until three typed Pokemon or dual items are introduced this sort of gimmicky sets will be your lot. And I would arguee that these sets have been far to compromised to be called viable. I would much rather recommend using two or even three Pokemon to accomplish each task individually.
