<datalist>
Suggestions for a field that still accepts anything.
Linked to an <input> through the list attribute, it turns the field into autocomplete without a line of script. Unlike <select>, it restricts nothing: the options are a shortcut, not a closed list.
The price of that freedom is the appearance. The list is drawn by the browser and barely accepts CSS.
<label for="busca">Specimen</label>
<input id="busca" name="q" list="especimes">
<datalist id="especimes">
<option value="details">
<option value="dialog">
<option value="meter">
</datalist>