Using Country TLD to rank for Google.com

Have any of you guys used a .co.uk or .co.in for example to rank on Google.com ? I started a site some time back but it's a specific country TLD, now I want to rank a few pages for it on Google.com . I've never tried this before as I usually use .com's to rank on Google.com, but I'd love to hear your experiences if you have used country TLD's and whether it negatively or positively affects the rankings on Google.com.