Center letter: o
Outer letter: g i k n t u
Answers (50):
  unknotting
  ginkgo
  going
  gong
  gonging
  goon
  gouging
  gout
  ignition
  ingot
  into
  intoning
  intuition
  knot
  knotting
  kook
  noggin
  nonunion
  nook
  noon
  noting
  notion
  noun
  oink
  oinking
  ongoing
  onion
  onto
  outgo
  outgoing
  outgun
  outgunning
  outing
  togging
  toking
  tong
  tonging
  tonguing
  toning
  took
  toon
  toot
  tooting
  toting
  tout
  touting
  tuition
  union
  unknot
  unto