Try going for a (whatever ant is in latin) queen with the ability to infect others with worker-ant thingies. Oh, and her powers work 24/7. Epic by sheer numbers.

Ok.. if you really want to see plenty of JCV ideas, there is a thread (not the one I started) that has plenty of discussions on the topic, including my own ideas. You may want to add yours to it if you want.

Sorry if I made this unclear: The player IS the spirit. I found this to be really interesting, so I wanted to try it, but I wanted to get other people's opinions beforehand.

I was thinking a bit, and looking at this power in the custom powers section gave me the idea for a challenging and fun character to play: A spirt stuck in some person's head.

Bound Spiritual Entity [+3]
Description: You are a spiritual entity imprisoned in a physical object, you have no body, and cannot act in the physical world without a bearer.
Effect:
Unbodied. You cannot take physical skills,  you cannot move yourself, and you cannot communicate verbally and other neat things.
Communicate with Bearer. You are able to telepathically speak with the bearer of the object you are tied to.
License to Possession. If you have the domination ability, you qualify for the possession upgrade, and you can possess your bearer.
Called to Bearer [-1]. You have the ability to tie yourself to the bearer of your physical prison, and you can teach them to call your prison to their hand.

Switch the "in a physical object" to "in some dude's head" and give yourself a couple powers I made up:
Empowering Spirit -1
You cannot take powers yourself, but you can give them to the person you are bound to. Any powers/stunts you have (unless they say otherwise) are conveyed to your host.
Creature of Spirit-1
 You have no body, and as such, you are unable to be "hit". Eliminate your physical stress track and add 2 boxes to your mental stress track. Magic made to target spiritual beings can hit you, and fire can damage you, but you take it to your mental stress.
At this point you can give your "bearer" powers in order to assist him/her. Maybe you have the ability to take over your "bearer" in a fight, and assist hiim. I think this would be really fun to play.. please give your opinions.

I'm GMing a game, and my players seem to want to be action heroes, and one of them has asked me several times if he could throw thugs at other thugs. Anyone have any idea how I should go about this? Or should I do it at all?

If you're doing rome, bring in romulus and remulus. Mabye the wolf that suckled them was in fact a spirit or were-form of some kind, and is still alive. Maybe Remulus' spirit still roams Rome. Also, bring in the possibility of a nearby phantom city (the one that remulus was going to create) in the nevernever.

Looking at some of the topics around here about converting manga characters to DFRPG reminded me of something I've been wanting to do for a while: convert one of my favorite mangas (Black Cat) to a playable DFRPG campaign. I kind of want to start by statting some of the characters. Here's a quick list.
Train Heartnet (with "railgun").
Sven Vollfield (With glaspar eye).
Train (beginning of series)
Sven (beginning of series)
Eve (End of series)
Rinslet Walker
Chronos #s (janus and #10 in particular)
Tao Masters (any of them really)

Shadow Manipulation [-1]
This reminds me of some powers I helped set up for a shadow-user I GMed.
Dark Void -1
Effects: You can increase the shadows within a zone. Add the aspect sticky aspect Increased Shadows, by using discipline. This can be opposed by a counterspell.
Myrrk Void: Your shadow-increasing skills rival the Myrrk itself. Give a +1 to attempts to create shadows, and add the aspect Near-Myyrk alongside Increased Shadows.
Shadow Warp -2
You can travel from shadow to shadow with a distance up to one zone. This requires no roll, but in order to escape into the shadows while being attacked use Athletics. When emerging from the shadows, roll stealth against all nearby enemies' alertness. If you succeed, you gain a relevant aspect. If not running away, you may then make an attack as a supplametal action. (Yes, you can warp into an enemy's shadow).