Is there an Input Filter without built-in restrictions?
You can always just make your own text filter through the admin.

If you head to /admin/config/content/formats and click "+ Add text format," you'll be able to customize your own text format, which includes the roles who can use it, what filters you would like to use (using none should allow for any html tag to get through).

If there are some html tags you don't want showing up in your text format, use "limit allowed HTML" tag, and list the tags you want, like this:

&lt;a&gt; &lt;em&gt; &lt;strong&gt; &lt;cite&gt; &lt;blockquote&gt; &lt;code&gt; &lt;ul&gt; &lt;ol&gt; &lt;li&gt; &lt;dl&gt; &lt;dt&gt; &lt;dd&gt; &lt;blink&gt;


You could event throw (as your example) a  tag in there to let it through. There is however, one big warning I need to leave you with:

====================WARNING ========================

Allowing users to place javascript on your page is a huge, huge security threat. If you decide to give users this privilege, make sure it's only with people you absolutely trust. If a text field allows JS to be placed in it, your basicly opening a door for a cross site scripting atttack.

Same holds true for the PHP filter, in fact the php filter is going away in D8, so I would really advise against using that.