Optional case-sensitive search.
Option to search for special characters — including line-feed, tab — within a phrase (e.g. "this: that").
Search for pages of a certain rank only (e.g. a Google PageRank delimiter).
Returning only pages with a certain amount of linked file-types (e.g. to search only MP3 directories).
Returning pages of certain word-quantity only (e.g.: keyword + words[500-1000]).
HTML/ XML-Doctype search (e.g. search RSS-Feeds or XHTML only).
Full page-source phrase search (including HTML).
Search through content within a given HTML-element or attribute only (e.g. "form", "h1", "a", "cite", "alt").
Searching for meta-data (like author).
Searching through pages with a certain HTML-element quantity only (like "must have above 100 links").
Option to include keyword-variations/ synonyms in a search, or to have new keywords suggested.
A wild-card operator for an unlimited number of words (like "this *[1-20] that").
Easy-to-use date delimiters ("return only pages that changed yesterday").
Indexing of very recent documents, and very frequent updates.
Return pages with a given update-frequency only (like "must have daily changes").
Search through recently added URLs/ domains only.
Practically unlimited number of keywords/ phrases.
Flexible wildcard operators for sub-strings.
Finding content without page-size limit (e.g. Google's 100K indexing limit).
Searching through all parts of the search engine at once (e.g. "News", "Groups").
Receive 1000 or more results at once.
Full FTP-indexing.
Fuzzy "OR" search (e.g. return "Best-Of" keyword intersection).
Full boolean expressions with unlimited nesting.
Searching for links pointing to a domain, excluding the domain itself.
Searching within multiple sites, with optional exclusion of multiple sites.
Searching for images using image comparison algorithms.
Searching for music using music comparison algorithms.
Option to get thumbnail previews of listed pages, or to see previews of images from the page.
Option to "ban" a site in personal settings, so that it will be excluded from future results.
Option to list all meta-data on the Search Result Page (e.g. "author").
Ability to save different search settings.
Set result-description length and other result-formatting details, format page display.
Set own "Page Rank" definitions/ parameters.
Sorting result by date, page size, in reverse order, and so on.
Specifically find pages with little text and lots of images, or vice versa.
Optional recording of search-history for later re-use.
Option to group result list into subject categories.
Having a programming interface for all the search engine's features (e.g. a Google Web API covering Image Search, Group Search).
High amount of automated API queries (e.g. much more than the 1000 daily requests to the Google Web API).
Explanation in result list of why a certain page ranks good, extensive query documention (including query limitations).
Macro-recording of multiple searches with option to edit and automatize Macro.
Very fast email response to questions asked, or moderated support discussion forum.
Comparing the cache-history for a given document (to see what has changed).
Option to pay a small monthly fee to enable search of otherwise restricted databases (the "Deep Web").
Searching through content of mixed languages only (e.g. to find translations).
Query via hand-phone SMS, or by sending Email.
Even more playful gimmicks, like special-occasion logos, April Fools jokes, result randomization, competitions and events.
Viewing the last [N] entered search queries (like AllTheWeb's feature), or see similar queries by others for a given search.
Provide search-toolbar for currently unsupported Operating System/ Browser [X].