Although one thing this fake list got right was making a lot of new type combinations. I started writing down all of the combinations that Pokemon is missing and I had to stop because I ran out of room on the paper. 
Seriously though, we need a Dark/Steel type!
EDIT: Here's a list of Pokemon type combinations that haven't been used:
Bug/Dark-
Bug/Dragon-
Bug/Electric-
Bug/Fire-
Bug/Ice-
Bug/Normal-
Bug/Psychic
Dark/Dragon-
Dark/Electric-
Dark/Fighting-
Dark/Ground-
Dark/Psychic-
Dark/Steel-
Dragon/Electric-
Dragon/Fighting-
Dragon/Grass-
Dragon/Ice-
Dragon/Normal-
Dragon/Poison-
Electric/Fighting-
Electric/Fire-
Electric/Grass-
Electric/Ground-
Electric/Ice-
Electric/Normal-
Electric/Poison-
Electric/Psychic-
Electric/Rock
Fighting/Ghost-
Fighting Ice-
Fighting/Normal-
Fighting/Rock-
Fire/Ghost-
Fire/Grass-
Fire/Ice-
Fire/Normal-
Fire/Poison-
Fire/Psychic-
Fire/Water-
Flying- *Arceus does't count*
Ghost/Grass-
Ghost/Ground-
Ghost/Normal-
Ghost/Psychic-
Ghost/Rock-
Ghost/Steel-
Ghost/Water-
Grass/Normal-
Grass/Steel-
Ice/Normal-
Ice/Poison-
Ice/Rock-
Ice/Steel-
Ground/Normal-
Normal/Poison-
Normal/Rock-
Poison/Psychic-
Poison/Rock-
Poison/Steel-
