Brown meat over medium heat. Once it begins to release juices, add onion, bell pepper, jalapeños and garlic and cook, stirring frequently. Add tomatoes, pumpkin, water, chili powder, cumin, salt and pepper and bring to a boil. Reduce heat to medium low and add beans. Cover and simmer, stirring occasionally, for 30 minutes more. Add some frito chips to a bowl. Ladle chili over the fritos and top with sour cream and sharp cheddar cheese.