I'm looking to get an .es domain. Just wondering how this might impact search results and rankings as I'd like to make the website available worldwide.
It does make a difference. All TLDs are treated equally in a google.com web search.
However, TLDs do affect your search results for country specific searches. For example, a .me or .tv domain will not rank as well as a .us website in a google.us web search. Also, a .co.uk site will rank better then a .us site in a google.co.uk search. This is because country specific searches give precedence to local websites.
So if you are targeting a specific country or region, try to use the TLD for that country or region. If not then the TLD does not make a difference.