Only in localised searches. There is some benefit to targeting the extension to your target market. A .co.uk for example will rank better in the UK ... etc..
No Effect at all... Google doesnt really care about it. It's individual's choice and our choice made .com familiar.
Your chances of ranking well in the local search results are higher if you have a domain extension corresponding to that country as Scottwood said. A .de would help you rank better in Germany, a .com.au in Australia, and so on.