Not just humor, but the overall tone of your application essay is remarkably important. It's also difficult to get right. When you are asked to write about your accomplishments, those 750 words on how great you are can make you sound like a braggart. Be careful to balance your pride in your achievements with humility and generosity towards others. You also want to avoid sounding like a whiner -- use your essay to show off your skills, not to explain the injustices that lead to your low math score or failure to graduate #1 in your class.
I advise students to read plenty of examples of strong essays in advance of beginning any brainstorming or writing. There are a number of books on the market and websites to help. Then I like to choose a couple of those sample essays and have the student identify three things or traits that were revealed about the writer/applicant. For example, family is important as revealed by the catchy beginning that showed the writer/applicant having a deep discussion with an older sibling. Or the writer is profoundly interested in studying French and is willing to take on challenges outside her comfort zone as revealed by the reference to studying abroad in a full-immersion exchange program. Or the writer values community as revealed by the eloquent description of her role within the corps d’ ballet, and how she provides support to and draws on the strength of her fellow dancers. Then I ask, “what do you want to reveal about yourself that’s important to you?”
This is one of the most extensive and helpful posts I’ve read on how to write college admissions essays. My feeling is that most English teachers know their great literature, but are not as versed on teaching writing–especially narrative style pieces. I agree that the best place to get ideas for unique topics, as well as learn how to structure these more informal essays, is by reading what others have written. You have collected a wonderful assortment of sample essays. Reading excellent writing, especially the New York Times, is also very helpful, especially feature-style articles that use creative writing techniques, such as anecdotal leads and descriptive details. I try to share similar writing advice on my blog, Essay Hell.