I can't even begin to choose. I was a freelance grant writer about 10 years ago and am looking to break back in to the world of fundraising. I've raised money for small welfare-to-work programs, school improvements, Planned Parenthhod, micro financing programs, children's theater, local PBS and NPR affiliates, animal shelters, food banks and organizations that train developmentally-disabled adults to get and keep jobs in the "mainstream" sector. Just to name a few. ;)
It's an incredible feeling to secure funding for a project because I told the most compelling story--grant writing is one of the best ways to hone your storytelling skills. You must be respectful of the other organizations asking for funding from the same finite pool of money--don't diminish the work they're doing in order to make your project seem more deserving of grant money. So, no, I really can't choose.