I'm doing a monotype run through X with a friend. He's

>>27419527
You'll need a crobat for fly, dragalge or tentacruel for surf (or one of the nidos), just for in-game utility.
The rest is up to you but nidoqueen/king are always fun to have around, toxicroak as well and it can deal with steel types, skuntank and drapion have a useful immunity to psychic. You can round things off with gengar (for levitate) and any of the myriad of grass/poison or bug/poison pokémon.
It actually is one of the comfiest type to do a monorun with.
Have fun OP

Dragalgae will be a good mon for your run through. Weezing maybe, Scolipede, Crobat so you have a flying mon. Skuntank would handle the Psychic weakness. Sixth...do you have a favorite poison type?

Ice should work, though perhaps electric or fairy instead to make it a bit harder to choose a team.

>>27419527
Nidoking, Crobat, Tentacruel, Venasaur, Gengar, Venomoth

>>27419715
Drop venemoth and tentacruel
Add toxicroak and dragalge

Definitely need a Toxicroak
Strength against steel types is useful

>>27419527
My recommendations:
>Crobat
Like someone else said, it's good for Fly. It's also fast and a decent physical attacker.
>Skuntank
Again, like someone else said, it has an immunity to Psychic. It also can learn Flamethrower/Fire Blast to take care of defensive Steel types.
>Toxicroak
Another good physical attacker, but unlike Crobat, Toxicroak can boost with Swords Dance. Its Fighting STAB can deal with Steel and Rock types that aren't too physically defensive. It can also get Sucker Punch to deal with faster Psychic types.
>Dragalge
Good special attacker with great coverage options and reasonable bulk.
>Gengar
Same as Dragalge except faster and frailer. It gets Ghost/Fighting coverage.
>Nidoking
Solid mixed attacker. Great Atk with STAB EQ. Amazing coverage on the special side + Sheer Force makes up for its mediocre SpA.

>>27419527
don't be a rude dude, give him something nice. Grass and bug are comfy but tough, Rock and fire look alright, but honestly fighting looks the most based in this gen. I'd give him that

>>27419527
>>27420179
Ice type would be a great runthrough.
>Abomasnow
Hail + Grass STAB for Water and Rock types.
>Froslass
Snow Cloak + Fighting immunity.
>Aurorus
Refrigerate Return is no joke in-game.
>Mamoswine
Thick Fat for Fire neutrality. Amazing Atk.
>Jynx
Sleep move, good Spe, good coverage.
>Lapras
Great coverage and bulk.

It sounds like a pretty fun team, actually.

Toxicroak
this fucker destroys everything in my current Y run and you can get Croagunk pretty early in the game