A logo represents your business, not all businesses require one, however it is a good idea even if just a simple design to have an image to represent your business.
When you start a new venture, a business card is very handy tool as you can give them to potential customers to remember you for when they need your service or product. They are also useful to put on noticeboards in your local area to get your business noticed.
A flyer can be a quick reference guide to what your business has to offer that can be given out at expo's or trade events. Its a great way to summarise your business.
A brochure for a product or service can be great to give to potential clients or put in a window display. It will usually be a clean, crisp one page display of something you are wanting to promote.
A portfolio of options, designs or products that your business offers can be a great way to review choices when meetings with clients. You can open a professional portfolio of products for clients to review and choose from helping your client to make decisions.