These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
Ho Yay: A scene where Boone and Little Bear are so terrified of a huge booming noise that they hold eachother for dear life.
Nightmare Fuel: In The Key to the Indian, Omri and co. have figured out how to send themselves back in time to make past toys flesh. Omri's father ends up in a faceless Iroquois doll for a few hours.
At one point in time travel, Omri becomes a piece of fabric on an Indian tent, and when it catches on fire during a raid it begins burning him alive until his friends pull him back to the present.
Tear Jerker: Any of the times Omri and Patrick have to say goodbye to their little friends, but the send-off at the end of the first book stands out especially. Also, the deaths of Boone's horse, Tommy the World War I medic, and Tom the thatcher. Even Jenny's death told in flashback wrenches at the heartstrings.