Bonus points for reasonings

Avoided using Pokemon that are used by any character of significance such as MC's, villains, professors, gym leaders, elite 4, champions, etc.
And/or plays a roll in competitive, and is generally forgotten.

Stantler:
>No interesting gimmick
>suffers extremely from "design creep"
>no competitive presence, >already limited in availability in-game

Sawsbuck:
>it's only memorable gimmick is forever trapped in a decade old game.
>Just a re-hash of Stantler down to the stats, concept and viability
>Outshined by it's own pre-evolution in terms of popularity.
>design is bland

Volbeat and Illumise
>Designs don't hold up at all.
>No competitive viability
>Signature move is better used by Manaphy
>The only other gimmick it has it better expressed by a plethora of other Pokemon
>Mono-Bug

Maractus
>Everything stated above
>No unique design gimmick
>No unique gimmick at all
>Severly outclassed by the other grass types in Gen 5
>Even worse re-hash of the Cacnea line.