Fruit and vegtables are nice but i rather have real food. Best snack is just backing some meat with lots of spices and next to this a small salad or a crazy omelet with some really dark and stiff bread.
Best snacks are low cal, high fullness factor so check out:
This is a list of the most nutritious food that is also the most filling.
Try to go Paleo is you can handle the change. Eliminating gluten and carbs will work wonders and you can eat pretty much all the veggies and meat you want.