Longshot is (allegedly) not a mutant, Danger is a robot, Daytripper was a member of the Muir Island X-Men so i guess she counts (she's just a witch). Also from that team, fully human: Tom Corsi, Sharon Friedlander and Alysande Stuart. The Nurse at the X-Mansion, Annie Ghazakanian, had a mutant kid but she was not a mutant herself. To name some aliens, Warlock, Kid Gladiator, Warbird and Broo do not have an X-Gene. Also, Deathlok was part of X-Force and he's not a mutant.

Juggernaut

There is actually a lot of non-mutant members.

Longshot is the son of a mutant (who is also his son, Shatterstar), but not a mutant himself.

Ink isn't a mutant, but actually a guy who was tattoed by a mutant tattoo artist. The tattoo artist was the mutant with an ability to give powers through tattoos. Tattoo himself is just a human.

Mimic isn't a mutant but a genetically engineered mutate. Though writers often change their minds about that.

Warbird wasnt a mutant but just a member of the shi'ar. She joined the xmen to watch over Kid Gladiator.

Danger was a mutant machine but not an X-gene mutant.

Warlock was a mutant machine but not a mutant.

Deadpool isn't a mutant but a mutate.

Cloak and Dagger were xmen but not mutants.

There's been a lot, I'm definitely missing some.