One of the many features that got me into playing and loving Shadow Warrior is its weapon arsenal.
I think it's awesome. We got fists, shurikens, a freaking Katana blade, dual wielding UZI's, a rocket launcher with three firing modes, one being a huge-ass nuke! and so on.

My personal favs are the bad ass looking Riot Gun, with the barrels that makes it look rather like a chaingun.
Throwing shurikens is fun too, I prefer doing that before using the UZI's tbh.

But one that really sticks out, is the Ripper Heart. Still beating in your hand.
The Guardian Head looks cool too, but a bit too static. However, the Head's firing modes makes sense.
The Ripper Heart on the other hand, don't.
When you squeeze the heart an ghost like replica of you is summoned, armed with a Rail Gun.
As a kid, this really dissapointed me. Still does actually. Would be cool if the heart acted more like the Voodoo Doll in Blood but only on Rippers and those other tiger looking fiends.

What do you think?

Both gorilla and tiger like enemies are Rippers, but there are male and female types (if you didn't noticed even big mature ones have two different sprite sets). When Ripper kills you they tear up your heart out of your chest to get your strongest power, so you, using Ripper heart doing the same - bringing your phantom with strong weapon.

Comparison to Blood is not the best one because in Blood there is no ultimate weapon while in Shadow Warrior normal ultimate weapon is Rail Gun (nuclear warhead is only alternate mode to missile weapon so doesn't count as a separate and isn't very effective to boss and mini-boss types, only partially).

Seems FWH actually listened to my prayers. The Demon Heart in SW '13 acts much like the Voodoo Doll does in Blood.
But from what I've heard, the Heart is able to kill more than just one enemy. How do I do this?

In the Beta/Alpha versions of SW the ripper heart actually DID act as a voodoo doll of sorts. You'd squeeze away and the enemy closest or aimed at would start getting wounded.

Obviously they changed it for the final release.

They've changed the Guardian Head as well. Not for the good however.
It is now more like an disposable item (also like the Demon Heart now) that, when all used up you can't use it anymore.
There's no other ammo for it other than finding another one, and unlike SW '97, the Guardians aren't everywhere.
The firing mode is cool though, it acts like a laser. But also, keep in mind that Painkiller: Overdose did this first and dare I say it? Even better. And again, unlike SW '97, where we had THREE firing modes to chose from, it's now only one.