It is really darn cute to hear him sort of stumble his way through, trying to get the sentence construction just right.
I know he's still evolving where this is concerned, and I have a feeling I should jot it down now because it may be only a fleeting thing.
So.... here are some examples:
"Mommy, push I!" (on the swing)
"Mommy, hold I!"
"It's I'm birthday!"
"Mommy, change I! I'm pants are wet."
"I'm daddy will like this." (What he observed when he received a "Daddy and Me" book for his birthday)