Might depend on the style sheet you have selected. For Article>Preprint I get a bullet, for example. Can be altered by editing the style sheet and changing the dingbat type, if you are into editing style sheets. Or you can explicitly add/change the dingbat from the Format window if you prefer not to mess with style sheets.

The default stylesheet certainly has the Item style. What stylesheet are you using? Also, if a given stylesheet does not have the menu item Format > Style > Item it may still have that style but set so that it does not appear in the menu. You can get a list of the styles contained in the style sheet--roughly--by doing something like the following.

Here is the list of paths to the standard style sheets shipped with Mathematica (note that it also includes directories which themselves have stylesheets, so to get at those one has to generalize this simple code):

FileNames[{"*"}, {FileNameJoin[{$InstallationDirectory, "SystemFiles",  "FrontEnd", "StyleSheets"}]}]

Let pick out the path to the Default.nb style sheet on my system and import its Notebook expression:

notebook = 
  Get["/Applications/Mathematica10.app/SystemFiles/FrontEnd/StyleSheets/Default.nb"];

Here is then a list of the styles defined in this style sheet:

Cases[notebook, StyleData[z_] :> z, \[Infinity]]

which gives

{StyleDefinitions ->  "Core.nb", "Notebook", "Title", "Subtitle", "Subsubtitle", \
"Chapter", "Subchapter", "Section", "Subsection", "Subsubsection", \
"Subsubsubsection", "Subsubsubsubsection", "Text", "SmallText", \
"Item", "ItemParagraph", "Subitem", "SubitemParagraph", "Subsubitem", \
"SubsubitemParagraph", "ItemNumbered", "SubitemNumbered", \
"SubsubitemNumbered", "Text", "SmallText", "Input", "InputOnly", \
"Code", "Output", "Message", "Print", "InlineFormula", \
"DisplayFormula", "DisplayFormula", "DisplayFormulaEquationNumber", \
"Program", "Reference", "Header", "HeaderSection", \
"HeaderSubsection", "HeaderTitle", "Footer", "FooterSection", \
"FooterSubsection", "FooterTitle", "PageNumber"}

The first item in this list, StyleDefinitions -> "Core.nb", points to the lower-level stylesheet that Default.nb depends on--it is in the list generated by the code above.