How to corrupt a database please???

[Nurudin Javeri]

Hi all, I am hiring a few new junior DBA's and I want to put them thru a 
simple db repair training.  Does anyone know how I can deliberately 
corrupt a MyISAM and InnoDB database in different ways please?  So what 
I want to do is corrupt 3 MyISAM 100gb databases, 3 InnoDB 100gb 
databases - ALL WITH DIFFERENT ERROR MESSAGES and have these newbies fix 
them in a 2 hour period :-)  I have fixed oodles of db's but NEVER 
thought I would see the say where I would WANT to corrupt a db on 
purpose, but that day is here and am looking for advise please.

Thanks...

Nunu