The idiomatic wording would be, "Advice needed for a presentation on rationality." Advice is a type of information, so making it plural is redundant. This is also why you never hear people saying, "I need your advices." (Or, for that matter, "I need your helps.")

EDIT: However, it's idiomatic to say, "I need your services," as well as, "I need your service." It could be that people who provide service generally provide possibly multiple types of service. The tenor of "I need your service" is more imperative, however. There's more of a presumption of the asker knowing what they want ahead of time, versus "I need your services." The above doesn't apply to advice/advices, however. It may be arbitrary.