This is a fun one.
I'd asked for the feature but didn't see if happening so I wrote it for all to enjoy.

Attempt to rob the bank.
Success = you get between 20% and 80% of the banks total money, all users loose that percentage, you loose 10 karma.
Failure = you loose 100 karma, you loose all your credits.
I have mine set to 1000 credits to purchase and 20% chance to win, users on my site have lots of credits because I've backpaid everyone for past posts.
<?php/**********************************************\| SMFSHOP (Shop MOD for Simple Machines Forum) || (c) 2005 DanSoft Australia || http://www.dansoftaustralia.com/ |\**********************************************///File: RobTheBank.php// % chance to steal from all members in the bank// on success, awards robber between 20 and 80% of the sum of all bank accounts// and reduces bank accounts accordingly and gives 10 negative karma.// On failure, gives -100 karma and sets money and bank money to 0 for robber.//VERSION: 1.0 (Build 1)//DATE: Sep 26th, 2006// $Id: RobTheBank.php chadk $class item_RobTheBank extends itemTemplate { function getItemDetails() { $this->authorName = "Chad"; $this->authorWeb = "http://www.aviary.info/"; $this->authorEmail = "generalchad@gmail.com"; $this->name = "Rob the bank!"; $this->desc = "You can try to ROB THE BANK! This gives you a CHANCE to steal a portion of the money from EVERYONES bank account! Note: Karma is NOT BLIND! Even if you rob the bank, there may be consequences!"; $this->price = 1000; $this->require_input = false; $this->can_use_item = true; } //see AddToPostCount.php for more infos function getAddInput() { return "Probability of successful robbery: <input type='text' name='info1' value='10'>%"; } function onUse() { global $db_prefix, $ID_MEMBER, $item_info, $user; $pmfrom = array( 'id' => 1, 'name' => 'Chad', 'username' => 'Chad' ); $pmto = array( 'to' => array(1), 'bcc' => array() ); //get a random number between 0 and 100 $try = mt_rand(0, 100); //if successfull if ($try < $item_info[1]) { //get stealee's money count $result = db_query("SELECT sum(moneyBank) as vault FROM {$db_prefix}members", __FILE__, __LINE__); $row = mysql_fetch_array($result, MYSQL_ASSOC); //get random amount between 0 and amount of money stealee has $steal_amount = 1-(mt_rand(10,60)/100); //take this money away from stealee... $result = db_query("UPDATE {$db_prefix}members SET moneyBank = moneyBank * {$steal_amount}", __FILE__, __LINE__); //...and give to stealer (robber)$steal_amount = ($steal_amount-1) * -1 * $row['vault']; $result = db_query("UPDATE {$db_prefix}members SET money = money + {$steal_amount}, karmaBad = karmaBad + 10 WHERE ID_MEMBER = {$ID_MEMBER} LIMIT 1", __FILE__, __LINE__);sendpm($pmto, 'Bank Robbed!', "{$user} Robbed the bank for {$steal_amount}", 0, $pmfrom); return "You ROBBED THE BANK for $steal_amount! Thief! Your Karma is STILL reduced by 10! (Karma isn't blind!)"; } else { //if reducing Karma doesn't work, replace //'karmaBad = karmaBad + 10' with 'karmaGood = karmaGood - 10'$result = db_query("UPDATE {$db_prefix}membersSET karmaBad = karmaBad + 100, money = -100, moneyBank = -500WHERE ID_MEMBER = {$ID_MEMBER}",__FILE__, __LINE__);$result = db_query("DELETE FROM {$db_prefix}shop_inventoryWHERE ownerid = {$ID_MEMBER}",__FILE__, __LINE__);sendpm($pmto, 'Bank Robbery Foiled!', "{$user} was BUSTED!", 0, $pmfrom);return "Steal <b>unsuccessful!</b> You Karma is now reduced by 100!"; } }}?>