What It Scores
MI is a valid word in the tournament list this site uses. Tile values only, before any premium square: 4 in Scrabble, 4 in Words With Friends, 4 in Wordfeud. The letters break down as M3 I1.
Longer Words Containing MI
MI appears inside each of these, which is what makes it worth knowing as a hook.
Next: the Word Unscrambler for any letters at all, and the two and three letter lists. Full entry and definition at Merriam-Webster.