With each player in a game of Scrabble or Words With Friends getting 7 letters at a time on their rack, 6-letter words can play a huge part in deciding who will win and who will lose a game.
The 6-letter words containing IN on this list are worth 9.8 points on average.
But the best of the lot is worth a grand total of 24 in a game of Scrabble and that word is QUINZE.
If none of the 1891 words on this list meet the criteria that you are looking for then you may find some success with similar lists: 6-letter words starting with IN, 6-letter words ending in IN and words with IN.