Regarding freelance web sites: Sometimes there are options to represent yourself as a group of freelancers; a team if you will. The advantages of doing so are clear. I work alone. I can't find fellow freelancers who'd want to team up with me. I'd like to create a virtual team, so to speak, but that would be lying. Now, if I possess the diversity of skills that would be required of an entire team would it be considered unethical to represent myself as part of a team?
Are you alone? Then 'we' is misrepresentation, and at some point during a project it will become clear that you are in fact alone and the client will find out. It may not mean the end of a contract when they do, but you can rest assured a client will take note to verify every other statement you make to ensure there is no further exaggeration or 'creativity'.
Unlike one of the other answers, I don't see how being creative with the truth is anything else than a euphemism for lying. And the old 'but everyone is doing it' is no excuse either. Not to mention that you can ask yourself which looks better: an incredibly versatile freelancer or a team of 3 or 4 with limited skill sets.
Now I am no saint, in the beginning of my freelance career I tried exactly the same sort of 'creativity' you mention, and it never worked out. Just stick to the truth and you'll see things remain simple, straightforward and customers trust you.
+1 to user3244085's answer because I was going to write an answer saying exactly the same things.
But also I want to add that if a single freelance says that he is a team of 5 people (when is 1), that can be appealing at first but also means that the client expects a "work power" of at least 200 hours per week (assuming 8 hours x 5 days x 5 people), a single freelance will never be able to work that much even without sleeping because 200 hours / 24 are 8,3 days per week which is impossible. The client will not see any problem while he asks for small jobs but there will be big troubles when the single freelance will not be able anymore to handle bigger projects.
I strongly always encourage to be clear and transparent with the client, first for personal work ethics, second because lies or "creative truth" is very hard to maintain in time, sooner or later the client will discover the lie and that is very bad for the work relationship and personal reputation.
If you have more skills present yourself genuinely for what you are in work terms, be clear in describe yourself and your knowledges.
I agree with all that has been said, that you should never lie, you will just look like an idiot when you are discovered. But I wanted to add this, that you can see good things about being an individual. For instance...
"As an individual I can react and respond quickly and authoritatively to every request, every situation and under all circumstances."
"As a specialist and an expert in my field, I have developed a network of other expert consultants, designers and developers that I can call upon for assistance at any time, so should anything arise I cannot personally deal with, you can be certain that I will have the channels at hand to cope with any challanges that may arise" Now here you are saying you are a member of stack overflow, without actually saying it, or have access to peopleperhour, or any other online forum where you can discuss issues, find answers or sub contract work out to.
You do not have to lie. You should be proud of what you are right now, and sell the benefits that brings. For instance many clients like to know that to you, they are the single most important thing in the world. Their project really matters to you and its success is your success too. As opposed to an agency that needs to bring on X number of new clients or sell X amount of deals every week just to pay for the offices and the wage bill.
Honesty will pay you far more in the long run than any deceptively gained contracts. Been there, done that, learned that honesty pays.