Odd One Out

[RuFF]

Sableye, Pawniard, Sneasel.

Sableye is the only one with a mega form. (FYI was released as a mega pokemon a few weeks ago)
--OR--
Sableye doesnt have an evolution.

You didn't put any choices so I'm going to put it my self

Bite, Charm, Growl

 

[Nah]

You didn't put any choices so I'm going to put it my self

Bite, Charm, Growl

It's suppossed to be Pokemon, not moves. But to keep this going: Bite is the only one that inflicts damage.

Charizard, Servine, Marshtomp

 

[Juno]

Marshtomp cannot learn Aerial Ace.

Zoroark, Granbull, Lucario

 

[Hiatus]

Zoroark is the only one that could transform itself.

Feebas, Magikarp, Luvdisc.

 

[Yato]

I can think of three possibilities:

1. Luvdisc doesn't have an evolution.
2. Magikarp can't learn any TMs or HMs.
3. Magikarp is not a Gen. III Pokemon.

Magby, Elekid, Smoochum.

 

[Sapph the Knight]

Smoochum is the only dual-type.

Arcanine, Houndoom, Mightyena

 

[Jon4567]

Arcanine.
It doesn't evolve by level.

Budew, Roselia, Roserade.

 

[Khoshi]

Roserade doesn't have Leaf Guard for a Hidden Ability.

Mega Gardevoir, Mega Pinsir and Mega Ampharos.

 

[Jon4567]

Mega Gardevoir is the only one that doesn't change type from its original form.

Torchic, Chimchar, Tepig.

 

[imas234]

Tepig is the only one that doesn't get flying type moves [torchic line gets peck and brave bird, chimchar line gets acrobatics]

quilava, charmander ,torchic

 

[Juno]

Quilava has not been distributed as an event Pokemon.

Rattata, Zigzagoo, Patrat?

 

[Trick 'r Treat]

Zigzagoon because it doesn't grow a large front tooth/teeth.
--
Alomomola, Barbaracle, Starmie

 

[Nah]

Alomomola, since its the only one who's name is spelled the same forwards and backwards.

Vivillon, Torchic, Pelipper

 

[BrandoSheriff]

Torchic can't fly.
-or-
Torchic is the only one with a gender difference.

How about...
Darkrai, Absol, Beedrill

(anything except typing. bonus points for one that has nothing to do with mega forms ;) )

 

[Hiatus]

Absol's the one standing out, as it doesn't fly or float.

What about Chespin, Charmander, and Totodile?

 

[Abby]

Totodile is the only one that evolves at level thirty.

Squirtle
Wartortle
Blastoise

 

[Apollo]

Blastoise can learn Hydro Cannon without events.

Watchog, Sigilyph, Liepard

 

[LeGreyfish]

Sigilyph, because it has a dual-typing.

Unfezant, Swellow, Staraptor.

 

[Yato]

1. Swellow doesn't change appearance (even subtly) based on its gender.
2. Swellow is part of a two-stage line whereas the other two are part of a three-stage line.

Bidoof, Zigzagoon, Sentret.

 

[isthatyoudan]

Sentret for two reasons:
1. He's the only one standing on two legs.
2. The other two can learn the typical normal moves growl and tackle, while sentret cannot.
Okay... next up!
Minccino, Trubbish, Muk
This may be easy...