Unlike some other browsers, Opera makes it easy to disable Flash.
Quick and easy: Press F12 and make sure there is NOT a check mark next to ‘enable plugins’
Advanced: If you want to disable Flash without disabling other plugins, you can also go to
File > Preferences > File Types
and look for
application/x-shockwave-flash
you can then set Opera’s preference for what it will do when it runs into Flash.
Personally I have just edited the MIME type and file extension, so that
application/x-shockwave-flash
became
application/x-shockwave-flash_OFF
and swf became swf_OFF
which will make it easier to re-enable if I should ever so choose by editing them again, and it makes it easy to see what MIME types you have turned OFF.
If you are really, really sure, you could delete the MIME type entry altogether, but I don’t recommend that because it isn’t necessary and this leaves you with a fail-safe in case you need to re-enable.
You could also delete the NPSWF32.dll from your hard drive, but that too is overkill for some people.