Double B:
* bubble
* ebb
* obbligato
* rubber
* tabby
Double C:
* acclaim
* accuse
* occur
* success
* succumb
Double D:
* adder
* addendum
* bedding
* ladder
* muddle
Double F:
* affidavit
* effervescent
* off
* stiff
* waffle
Double G:
* egg
* eggplant
* aggression
* reggae
Double K:
* book
* cook
* look
* stock
* wreck
Double L:
* ball
* call
* doll
* full
* wall
Double M:
* hammer
* mammal
* mammmoth
* summer
* swimming
Double N:
* annoy
* funny
* run
* sun
* tennis
Double P:
* applause
* pepper
* sapphire
* supportive
* upper
Double R:
* arrest
* correct
* furry
* mirror
* terror
Double S:
* assess
* discuss
* grass
* miss
* possess
Double T:
* batter
* better
* butter
* letter
* mitten
Double V:
* vivid
* vividly
* vacuum
* velvet
Double W:
* awkward
* downward
* dwell
* shallow
* swallow
Double X:
* wax
* vex
Double Z:
* buzz
* fizz
* puzzle
* zigzag
Important Note: These are just a few examples! There are many more words with double consonants.