Perhaps you've been reading about Rolemaster and really like the idea of critical hit charts and the bloody, hilarious chaos they cause, but aren't sure you want to commit to a new system. Well, there's a way around that.
The book that governs all these wonderful critical for Rolemaster is called Arms Law, and true to the legacy of Rolemaster, is modular in nature. That means Arms Law can be easily adapted with a number of systems. At the time that the last edition of Arms Law was published, it contained rules for converting the system to AD&D. With that, it is easy enough to translate it to any several similiar classical games.
However, if you're playing something other than AD&D, you can still use Arms Law with a number of other systems. This free download by Iron Crown details Arms Law conversions for a number of other systems, to include:
-D&D 3rd Edition
-Legend of the Five Rings
-World of Darkness (including Werewolf)
The AD&D notes are also included in the free download. What's more, there are conversions for using Arms Law with such systems as Castles & Crusades and ICE's own High Adventure Role Playing (HARP). Older editions also had conversions for the HERO System, but I can't locate it at the moment.
For about $16 for a print copy or $8 for a pdf, you can have all the heartache and crunchy, painful, thrilling goodness that comes with Rolemaster's critical hit charts without having to leave the comfort of your own game.
My advice? If it sounds like fun, try it. There's a reason Rolemaster's critical hits are alternately revered and cursed in the RPG community.