With the normal grep command there is an --exclude option (covered in detail here: Use grep --exclude/--include syntax to not grep through certain files) that lets you ignore specific files when you are grepping.
Ack's --type option takes care of 95% of the cases where you'd want to exclude files, but it doesn't (as far as I can tell) handle the case of excluding a specific file. I've got a compiled JS file that has the contents of every other JS file in it (on a single line), so every time I grep for anything I get back the entire contents of that giant compiled file.
I'd hate to have to give up on ack and go back to grep over this, but it is really annoying. Please, someone tell me there's a way to exclude specific files from ack searches.
No, ack 1.x will not let you exclude a single file. In ack 2.0, you can. ack 2.0 was currently in its first alpha is now the current recommended version of ack.
As far as your specific case of the minified Javascript file, what version of ack are you using? ack 1.96 should ignore minified JavaScript based on extension. If the extension check doesn't work, you could probably hack ack itself, since it's a single Perl program. You can hack the is_searchable function.
In ack 2.0, we're looking at ignoring any line over, say, 500 characters because it's clearly not source code.
You may also want to join us on the ack-users mailing list. We're pretty responsive.