Case in point, is there a movie where a cat has died and has left theaters filled with people crying like a a little girl? No? Yeah, I agree.
How about dogs? There are tons of them!! Lady and the Tramp. The Fox and the Hound. Eight Below. White Fang. Iron Will. Where the Red Fern Grows. Marley & Me. And who can forget... Old Yeller!
I like books where the main characters have a familiar or similar type of companion. My advise to you: make it a dog! And if it has half the character my dog does you are going to win the hearts of your readers.
Decisions!All good books have a theme to them. One of my favorite themes is how a person is defined by their choices, not by their power. For instance, Harry Potter and Volde--- He-Who-Must-Not-Be-Named have a lot of similarities between each other:
Both were chosen by the same kind of wands (with the phoenix feather core from the same phoenix)
Both viewed Hogwarts as their real home
Both have bad tempers
Both are parceltongues
Both are only children
Both were orphans
Both were raised in homes where they were despised
Both are powerful wizards
Both are very inventive, inventive, cunning, and creative
Both were very determined
Both had a disregard for rules
But what made them different was their choices. Harry's choices were noble and selfless while Voldemort's were quite the opposite. This lead to them having very, very different destinies.
I love this theme. It is one of my favorites. It is an excellent theme to work into your book if you are currently looking for one.