Common words:
* Il (he, it)
* Ils (they, them, he, it)
* Ici (here)
* Il y a (there is, there are)
* Impossible (impossible)
* Important (important)
* Image (image)
* Impression (impression)
* Indépendamment (independently)
* Individuel (individual)
* Infini (infinite)
* Information (information)
* Initial (initial)
* Intéressant (interesting)
* Inutile (useless)
* Isolé (isolated)
Less common words:
* Iguane (iguana)
* Idée (idea)
* Idéal (ideal)
* Idylle (idyl)
* Ignorer (to ignore)
* Illustre (illustrious)
* Imagination (imagination)
* Impatient (impatient)
* Imprimer (to print)
* Incroyable (incredible)
* Indigène (native)
* Infiniment (infinitely)
* Innommable (unspeakable)
* Insolite (unusual)
* Invisible (invisible)
* Invité (guest)
* Irrésistible (irresistible)
* Isolant (insulating)
Remember: This is just a small sample. There are many more French words starting with "I" depending on the context.