As discussed in Ideas (http://ideas.salesforce.com/article/show/69729) here's a solution we have used for clients to enable customisation of the Clone button on Opportunities. This can be used to selectively choose which fields to copy and set default values:

For full details and the code to clone opportunity Line Items please contact me directly. We will be re-writing this in VisualForce over the coming months to make it futureproof.

Steps to Implement - Admins only

1. Setup -> Customize -> Opportunity -> Buttons and Links

2. Create new custom button called Clone, behaviour is Execute Javascript, Display Type Detail Page Button.

3. Paste in the code below and edit to match your requirements.

4. Remember to add the new button to the Opportunity page layout(s) and hide the original Clone button.

4. Test!

// Copyright 2008 BrightGen Ltd - All Rights Reserved try{ {!REQUIRESCRIPT("/soap/ajax/14.0/connection.js")} // ** EDIT THIS QUERY TO LIST THE FIELDS YOU WANT TO COPY ** var result = sforce.connection.query("Select o.Type, o.StageName, o.Product_Type__c, o.Planned_Opportunity__c, o.MarketSector__c, o.CampaignId, o.Business_Unit__c, o.Amount, o.AccountId From Opportunity o WHERE o.Id = '{!Opportunity.Id}'"); var newOpp = result.getArray("records"); // Reset the Opp Id and reset fields to default values newOpp[0].Id = ''; newOpp[0].Name = "Clone {!Opportunity.Name}"; // ** EDIT THESE FIELDS TO SET DEFAULT ANY VALUES ** newOpp[0].StageName = "1. Prospecting"; newOpp[0].CloseDate = new Date(2099, 0, 1); var saveResult = sforce.connection.create(newOpp); if (saveResult[0].getBoolean("success")) { newOpp[0].id = saveResult[0].id; alert("Opportunity cloned without line items"); } else { alert("Failed to create clone: " + saveResult[0]); } // Refresh the page to display the new oppportunity window.location = newOpp[0].id; } catch (err) { alert (err.description ); }