Index: source/blender/include/BDR_editmball.h
===================================================================
--- source/blender/include/BDR_editmball.h	(revision 10749)
+++ source/blender/include/BDR_editmball.h	(working copy)
@@ -42,6 +42,8 @@
  */
 void add_primitiveMball(int);
 void deselectall_mball(void);
+void selectinverse_mball(void);
+void selectrandom_mball(void);
 void mouse_mball(void);
 void adduplicate_mball(void);
 void delete_mball(void); 
Index: source/blender/src/editmball.c
===================================================================
--- source/blender/src/editmball.c	(revision 10749)
+++ source/blender/src/editmball.c	(working copy)
@@ -30,6 +30,7 @@
  * ***** END GPL/BL DUAL LICENSE BLOCK *****
  */
 
+#include <math.h>
 #include <string.h>
 
 #ifdef HAVE_CONFIG_H
@@ -40,6 +41,7 @@
 
 #include "BLI_blenlib.h"
 #include "BLI_arithb.h"
+#include "BLI_rand.h"
 
 #include "DNA_screen_types.h"
 #include "DNA_space_types.h"
@@ -225,6 +227,36 @@
 	BIF_undo_push("Add MetaElem");
 }
 
+/* should be put in some more reusable place and used in each "select random" */
+static void generate_pickable_list(int *list, int size, int pickamount)
+{
+	int i, j, removable;
+	
+	BLI_srand( BLI_rand() ); /* random seed */
+
+	/* generate list in form 0->1, 1->2, 2->3, ... i-2->i-1, i->0 */
+	for(i=0; i<size; i++) {
+		if(i == size-1) list[i]= 0;
+		else list[i]= i+1;
+	}
+
+	for(i=0; i<size-pickamount; i++) { 
+		removable= floor(BLI_frand()*(size-1)+0.5); /* with rounding. frand returns [0,1] */
+		
+		/* seek proper item as the one randomly selected might not be appropriate */
+		for(j=0; j<size; j++, removable++) {
+			if(list[removable] != -1) break;
+			if(removable == size-1) removable= -1;
+		}
+				
+		/* pick unwanted item out of the list */
+		list[list[removable]]= -1; /* mark former last as invalid */
+
+		if(list[removable] == size-1) list[removable]= 0;
+		else list[removable]= list[removable]+1;
+	}
+}
+
 /* deselect all MetaElements */
 void deselectall_mball()
 {
@@ -251,6 +283,51 @@
 	BIF_undo_push("Deselect MetaElem");
 }
 
+/* inverts metaball selection */
+void selectinverse_mball()
+{
+	MetaElem *ml;
+	
+	ml= editelems.first;
+	while(ml) {
+		if(ml->flag & SELECT) ml->flag &= ~SELECT;
+		else ml->flag |= SELECT;
+		ml= ml->next;
+	}
+
+	allqueue(REDRAWVIEW3D, 0);
+	countall();
+	BIF_undo_push("Invert MetaElem");
+}
+
+/* select random metaball selection */
+void selectrandom_mball()
+{
+	MetaElem *ml;
+	static short randfac= 50;
+	int amounttoselect, i= 0;
+	int *itemstobeselected;	
+
+	if(!button(&randfac,0, 100,"Percentage:")) return;
+
+	if(randfac == 0) return;
+	
+	itemstobeselected= MEM_callocN(sizeof(int) * G.totvert, "selectitems"); /* there might be a nicer way to get amount of metaballs */
+	amounttoselect= floor(randfac * G.totvert / 100 + 0.5);
+	generate_pickable_list(itemstobeselected, G.totvert, amounttoselect);
+
+	ml= editelems.first;
+	while(ml) {
+		if(itemstobeselected[i] != -1) ml->flag |= SELECT;
+		i++;
+		ml= ml->next;
+	}
+
+	allqueue(REDRAWVIEW3D, 0);
+	countall();
+	BIF_undo_push("Random MetaElem");
+}
+
 /* select MetaElement with mouse click (user can select radius circle or
  * stiffness circle) */
 void mouse_mball()
Index: source/blender/src/header_view3d.c
===================================================================
--- source/blender/src/header_view3d.c	(revision 10749)
+++ source/blender/src/header_view3d.c	(working copy)
@@ -1165,6 +1165,12 @@
 		case 2: /* Select/Deselect all */
 			deselectall_mball();
 			break;
+		case 3: /* Inverse */
+			selectinverse_mball();
+			break;
+		case 4: /* Select Random */
+			selectrandom_mball();
+			break;
 	}
 	allqueue(REDRAWVIEW3D, 0);
 }
@@ -1180,8 +1186,12 @@
 	
 	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, "Border Select|B", 0, yco-=20, menuwidth, 19, NULL, 0.0, 0.0, 1, 0, "");
 	
+	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, "Random...", 0, yco-=20, menuwidth, 19, NULL, 0.0, 0.0, 1, 4, "");
+
 	uiDefBut(block, SEPR, 0, "", 0, yco-=6, menuwidth, 6, NULL, 0.0, 0.0, 0, 0, "");
 	
+	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, "Inverse", 0, yco-=20, menuwidth, 19, NULL, 0.0, 0.0, 1, 3, "");
+
 	uiDefIconTextBut(block, BUTM, 1, ICON_BLANK1, "Select/Deselect All|A", 0, yco-=20, menuwidth, 19, NULL, 0.0, 0.0, 1, 2, "");
 		
 	if(curarea->headertype==HEADERTOP) {