This video shows the (best) ending of "Hotel Dusk Room 215". I think it's the best ending, because Mila comes with you and Kyle gives her 'Mila's treasure'. And at the end (after the credits) you see the secret scene where Dunning's daughter Jenny arrives (and she shows her face).
Note You can't get this ending on your first playthrough.
Here's a description of how to get Mila's Treasure
When you play the game a 2nd time, then Louie gives you a "mystery cassette tape" (I think in chapter 8). Listen to the tape in Louie's room and you hear a code. Write it down. Then at the end of the game, when you are in a room with a computer, you have to enter this code (but first you have to enter the real code and leave the room, then reenter and enter this secret code). You then get a message about a nostalgic secret in room 220. After you wake up in your room and some people talked to you, you can go into this room 220 to finally get mila's treasure.
Note You can't get this ending on your first playthrough.
Here's a description of how to get Mila's Treasure
When you play the game a 2nd time, then Louie gives you a "mystery cassette tape" (I think in chapter 8). Listen to the tape in Louie's room and you hear a code. Write it down. Then at the end of the game, when you are in a room with a computer, you have to enter this code (but first you have to enter the real code and leave the room, then reenter and enter this secret code). You then get a message about a nostalgic secret in room 220. After you wake up in your room and some people talked to you, you can go into this room 220 to finally get mila's treasure.