Merry and Pippin.
Both had benefited from Treebeard's Ent-draught, as described in "Flight to the Ford" (in The Fellowship of The Ring):
You are thirsty I expect. Perhaps you are also tired. Drink this!' He
went to the back of the bay, and then they saw that several tall stone
jars stood there, with heavy lids. He removed one of the lids, and
dipped in a great ladle, and with it filled three bowls, one very
large bowl, and two smaller ones. ...
Then when some of the company reunite later, in "The Field of Cormallen" (in The Return of the King):
But amidst all these wonders [Sam] returned always to his astonishment
at the size of Merry and Pippin; and he made them stand back to back
with Frodo and himself. He scratched his head. 'Can't understand it at
your age!' he said. 'But there it is: you're three inches taller than
you ought to be, or I'm a dwarf.'
[Gimli] 'But what did I say? Mortals cannot go drinking
ent-draughts and expect no more to come of them than of a pot of