If you have the Windows SDK installed, you can find the XAML source for all default styles (assuming you installed the samples) in:
%ProgramFiles%\Microsoft
SDKs\Windows\v6.1\Samples\WPFSamples.zip
The zip file contains a folder Core which contains AeroTheme, LunaTheme etc which contain the source for default styles. Unfortunately these files are pretty large (~8500 lines for Aero) and not very well structured or formatted (IMO).
The default control template for a ListViewItem looks like this:
<ControlTemplate TargetType="{x:Type ListViewItem}">
<Border CornerRadius="2" SnapsToDevicePixels="True"
BorderThickness="{TemplateBinding BorderThickness}"
BorderBrush="{TemplateBinding BorderBrush}"
Background="{TemplateBinding Background}">
<Border Name="InnerBorder" CornerRadius="1" BorderThickness="1">
<Grid>
<Grid.RowDefinitions>
<RowDefinition MaxHeight="11" />
<RowDefinition />
</Grid.RowDefinitions>
<Rectangle Name="UpperHighlight" Visibility="Collapsed" Fill="#75FFFFFF" />
<GridViewRowPresenter Grid.RowSpan="2"
VerticalAlignment="{TemplateBinding VerticalContentAlignment}"
SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}" />
</Grid>
</Border>
</Border>
<ControlTemplate.Triggers>
<Trigger Property="IsMouseOver" Value="True">
<Setter Property="Background" Value="{StaticResource ListItemHoverFill}" />
<Setter Property="BorderBrush" Value="#FFCCF0FF" />
<Setter TargetName="UpperHighlight" Property="Visibility" Value="Visible" />
</Trigger>
<Trigger Property="IsSelected" Value="True">
<Setter Property="Background" Value="{StaticResource ListItemSelectedFill}" />
<Setter Property="BorderBrush" Value="#FF98DDFB" />
<Setter TargetName="InnerBorder" Property="BorderBrush" Value="#80FFFFFF" />
<Setter TargetName="UpperHighlight" Property="Visibility" Value="Visible" />
<Setter TargetName="UpperHighlight" Property="Fill" Value="#40FFFFFF" />
</Trigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="True" />
<Condition Property="Selector.IsSelectionActive" Value="False" />
</MultiTrigger.Conditions>
<Setter Property="Background" Value="{StaticResource ListItemSelectedInactiveFill}" />
<Setter Property="BorderBrush" Value="#FFCFCFCF" />
</MultiTrigger>
<MultiTrigger>
<MultiTrigger.Conditions>
<Condition Property="IsSelected" Value="True" />
<Condition Property="IsMouseOver" Value="True" />
</MultiTrigger.Conditions>
<Setter Property="Background" Value="{StaticResource ListItemSelectedHoverFill}" />
<Setter Property="BorderBrush" Value="#FF98DDFB" />
</MultiTrigger>
<Trigger Property="IsEnabled" Value="False">
<Setter Property="Foreground" Value="{DynamicResource {x:Static SystemColors.GrayTextBrushKey}}" />
</Trigger>
</ControlTemplate.Triggers>
</ControlTemplate>
Your best bet for removing all highlighting is probably to replace the ControlTemplate with you own that just includes the GridViewRowPresenter (maybe in a single Border). Don't forget to include the Trigger that greys the items when the control is disabled.