Place chicken breasts into bottom of slow cooker.
Sprinkle ranch dressing mix and half a package of the brown gravy mix over chicken. (You can use the whole package, but it might be a bit salty.) Top with butter pieces and desired amount of pepperoncini peppers.
Cover, and cook on low 4-5 hours or on high for 3 hours.
Remove peppers, and shred chicken.
Serve alone, on hoagie buns, or over rice, if desired.