This is probably one of the oddest SEO questions ever but here we go;
My site is showing up fine on the keywords I want but it is also showing up top on keywords that I don't want it to show up on. Is there any way to get Google etc. to get my site not to show up on certain keywords. I have full Webmaster Tools access to the site as well as access to sitemaps, robots.txt and the pages themselves

Regards,
Sam Rudge

I doubt there's any such way. Neither can showing up on keywords be controlled nor can not showing up. Anyways, it can get you some free traffic.
You may block certain pages from being indexed though using either the robots.txt or the 'noindex' attribute of the meta tag.

Hi,

Have you used those keywords in your meta or in copy of pages? If yes, then just remove those keywords from your website.

Yeep, it is indeed an odd question!

You can just change all your keyword and remove all the backlinks, but can I ask why?

I am very curious!

The problem is that I designed a website for someone and at the bottom I put
"Created by Sam Rudge"
When I search for "Sam Rudge" on Google the first result that comes up is that website where as I want MY website to come up first
Hope it is a bit clearer what I am trying to do now

Contact the webmaster and ask him to place the link to your site attached to the keyword "Sam Rudge" in that site.
Make sure its not 'nofollow'.
This will direct search engines to your site and within the next update, the keyword Sam Rudge should show up your site if the On-Page optimization is done properly.