diff --git a/.gitignore b/.gitignore
index 42dcc6e..57cf1b7 100644
--- a/.gitignore
+++ b/.gitignore
@@ -4,4 +4,5 @@ docs/.build
 docs/_build
 build/
 dist/
-mongoengine.egg-info/
\ No newline at end of file
+mongoengine.egg-info/
+env/
\ No newline at end of file
diff --git a/mongoengine/base.py b/mongoengine/base.py
index 9f54cd7..4523a26 100644
--- a/mongoengine/base.py
+++ b/mongoengine/base.py
@@ -410,8 +410,6 @@ class BaseDocument(object):
             value = getattr(self, field_name, None)
             if value is not None:
                 data[field.db_field] = field.to_mongo(value)
-            else:
-                data[field.db_field] = None
         # Only add _cls and _types if allow_inheritance is not False
         if not (hasattr(self, '_meta') and
                 self._meta.get('allow_inheritance', True) == False):
@@ -454,7 +452,8 @@ class BaseDocument(object):
         for field_name, field in cls._fields.items():
             if field.db_field in data:
                 value = data[field.db_field]
-                data[field_name] = value if value is None else field.to_python(value)                 
+                data[field_name] = (value if value is None
+                                    else field.to_python(value))
 
         obj = cls(**data)
         obj._present_fields = present_fields
diff --git a/mongoengine/fields.py b/mongoengine/fields.py
index d8d310d..dc5dbe0 100644
--- a/mongoengine/fields.py
+++ b/mongoengine/fields.py
@@ -66,6 +66,9 @@ class StringField(BaseField):
                 regex = r'%s$'
             elif op == 'exact':
                 regex = r'^%s$'
+
+            # escape unsafe characters which could lead to a re.error
+            value = re.escape(value)
             value = re.compile(regex % value, flags)
         return value
 
diff --git a/mongoengine/queryset.py b/mongoengine/queryset.py
index 00a7f7a..0b9218a 100644
--- a/mongoengine/queryset.py
+++ b/mongoengine/queryset.py
@@ -135,7 +135,6 @@ class Q(object):
 
         # Handle DBRef
         if isinstance(value, pymongo.dbref.DBRef):
-            # this.created_user.$id == "4c4c56f8cc1831418c000000"
             op_js = '(this.%(field)s.$id == "%(id)s" &&'\
                     ' this.%(field)s.$ref == "%(ref)s")' % {
                         'field': key,
@@ -239,6 +238,10 @@ class QuerySet(object):
         """An alias of :meth:`~mongoengine.queryset.QuerySet.__call__`
         """
         return self.__call__(*q_objs, **query)
+    
+    def all(self):
+        """Returns all documents."""
+        return self.__call__()
 
     @property
     def _collection(self):
@@ -667,11 +670,13 @@ class QuerySet(object):
         """
         key_list = []
         for key in keys:
+            if not key: continue
             direction = pymongo.ASCENDING
             if key[0] == '-':
                 direction = pymongo.DESCENDING
             if key[0] in ('-', '+'):
                 key = key[1:]
+            key = key.replace('__', '.')
             key_list.append((key, direction))
 
         self._ordering = key_list
diff --git a/tests/fields.py b/tests/fields.py
index ef776d4..1e53d23 100644
--- a/tests/fields.py
+++ b/tests/fields.py
@@ -674,7 +674,12 @@ class FieldTest(unittest.TestCase):
         PutFile.drop_collection()
         StreamFile.drop_collection()
         SetFile.drop_collection()
-        
+
+        # Make sure FileField is optional and not required
+        class DemoFile(Document):
+            file = FileField()
+        d = DemoFile.objects.create()
+
     def test_geo_indexes(self):
         """Ensure that indexes are created automatically for GeoPointFields.
         """
@@ -694,7 +699,7 @@ class FieldTest(unittest.TestCase):
         Event.drop_collection()
 
     def test_ensure_unique_default_instances(self):
-        """Ensure that every document has it's own unique default instance."""
+        """Ensure that every field has it's own unique default instance."""
         class D(Document):
             data = DictField()
             data2 = DictField(default=lambda: {})
diff --git a/tests/queryset.py b/tests/queryset.py
index b1f1657..b339d61 100644
--- a/tests/queryset.py
+++ b/tests/queryset.py
@@ -288,6 +288,13 @@ class QuerySetTest(unittest.TestCase):
         self.assertEqual(obj, person)
         obj = self.Person.objects(Q(name__iexact='gUIDO VAN rOSSU')).first()
         self.assertEqual(obj, None)
+        
+        # Test unsafe expressions
+        person = self.Person(name='Guido van Rossum [.\'Geek\']')
+        person.save()
+
+        obj = self.Person.objects(Q(name__icontains='[.\'Geek')).first()
+        self.assertEqual(obj, person)
 
     def test_filter_chaining(self):
         """Ensure filters can be chained together.