The Westing Game
Turtle manages to combine the plucky, feisty qualities of the traditional young adult heroine (think Claudia in From the Mixed-Up Files of Mrs. Basil E. Frankweiler, or, you know, Jo March from Little Women) with the hard-boiled determination of a Raymond Chandler detective (like Philip Marlowe, who's a classic example of a tough-guy problem solver). At the beginning of the book, it seems like she's got it tough in classic protagonist style: absent/cruel parents, a prettier older sister to be measured against, and a lot of pent-up anger. She wants to be a grown-up, and getting to play the game helps that happen. At the end, we glimpse her future and see a confident, smart entrepreneur – a real adult. In addition, one thing that Turtle values most is friendship, and she's someone we could totally see being friends with. Sometimes, that's a big part of what being a protagonist is all about.