I have tried to delete fields on objects such as Opportunities, as Salesforce has supposedly made it possible to do so in Schema Builder, but when I right click on the field and select 'delete' it doesn't remove it. I've tried all the major browser, so it doesn't appear to be a browser support issue.
fyi: these are also custom fields, that I'm able to delete in the settings panel, just thought it would make quicker work of it in schema builder.