Ight.. here we go for unused types. Some slightly inspired, others outright lazy.
>Normal/Poison
Zangoose - from being bitten and fighting Seviper so much, immunity n shit
>Normal/Rock
Dunsparce - drill tail used by people to dig through mountains n what not
>Normal/Bug
Sentret line - eating all them route 1 bug mons
>Normal/Ghost
Stantler - psychic powers from antlers are actually spirits
>Normal/Steel
Teddiursa line - defending dens against slow defensive ice types in winter
>Normal/Ice
Snorlax - Hibernation eating
>Fight/Ground
Conkeldurr line - nigga has 2 rock pillars
>Fight/Ghost
Mankey line - Gorilla in the mist shit
>Fight/Electric
Passimian - "football" is a Voltorb now like the Shellder on Slowbro
>Fight/Fairy
Mienfoo line - more angelic fighting style than other pure fighters
>Poison/Steel
Seviper - fangs harden to counter Zangoose adaptation
>Poison/Electric
Koffing line - poison clouds become static, thunder clouds
>Poison/Psy
Ekans line - reverse snake charmer shit
>Poison/Ice
Nido lines - colder climates (uninspired )
>Posion/Fairy
Trubbish line - eating so much steel trash built an immunity
>Ground/Fairy
Mudbray line - Mud Unicorn
>Rock/Ice
Sudwoodo - Christmas tree
>Bug/Psy
Kricketot line - Psychic music like Jigglypuff
>Bug/Ice
Shelmet line - Ice Armor
>Bug/Dragon
Pinsir - Cuz fuck you, he gets it
>Bug/Dark
Caterpie - night crawler motif
>Fire/Grass
Ponyta line - Forest fire prevention used by park rangers
>Fire/Ice
Magmar - dry ice kinda thing
>Fire/Fairy
Growlithe line - embrace the almost legendary/fairy tale lore in the universe
>Electric/Dark
Mareep line - from being used as light sources i.e. Amphrose as a light house
>Dark/Fairy
Zorua line - Theatrics and Kabuki shit n what not
Pic unrelated