Man, one thing leads to another, so here's another sidebar about mook rules.
This was inspired by my reading of the new webcomic, Lady Sabre and the Pirates of the Ineffable Aether, which is basically "Greg Rucka's the Swashbucklers of the Seven Skies Webcomic" (which is a pretty cool thing). It hasn't been going very long but the most recent strip reminded me very clearly of why I don't like mook rules.
Aside if you're unfamiliar: Mook rules are rules for handling the "nameless extras" in a fight, allowing large numbers of opponents to be put in play but be casually cut down by the hero. The term comes from Feng Shui, which is the daddy of this. Some people claim the less-than-1HD rules from AD&D are the basis of this, but the similarity is - to my mind - shallow and cosmetic.
You can go read it is you like - there are only 8 comics or so at this point - but to sum up, this is the point where we see the heroine kick the asses of multiple badguys at once without breaking a sweat. This is, theoretically, supposed to impress us with just how intensely badass and awesome the protagonist is, but in practice it tends to fall a little flat. Partly because it's so blatant, partly because it's so overused, it tends to feel like the author going "See! See!" more than anything which tells me about the character (which is, I note, an interesting contrast to the page before, which is both badass and says something).
There's a trick that bad writers use to make a character seem smart - they make everyone around them stupid. This is a terrible, lame, dissatisfying trick and mooks tend to be the badass equivalent of it. By making the opposition so trivial that they are casually knocked down, you don't make your protagonist look awesome, you just underscore how lame everything is.
This is not to say that mooks can't be done well, it's just that they're often not. One of the magnificent things about Hong Kong cinema was that it made fights with lots of guys seem awesome when compared to the same number of guys fighting John Rambo. There's a balance to strike - the opposition needs to seem dangerous enough that the protagonist's triumph does not seem inevitable. This same is true of games.
Games use mook rules for a variety of reasons, but there are three big ones: Genre simulation, Bookkeeping, and reinforcing awesome. Now, I have no real beef with the first two. If you want to model Hong Kong cinema, you need rules to model the big fights. Similarly, if you're playing a system where tracking a lot of lesser adversaries is cumbersome, a system for aggregating them can be a lifesaver. The problem is the last.
Mook rules rarely illustrate character awesome for the same reasons they can fail in fiction. Unless there's a sense of real opposition, then it's just a stylish pantomime. If that's what you're really looking for, then that's fine, but I point out that you're making a tradeoff to do it. Mook rules tend to do a great job of reinforcing the lethality of a system - hundreds of peopel get shot or cut down, after all! - but they often do so in direct contradiction to the way the rest of the system works. This is not a bad thing in its own right, but you need to realize that there is a cognitive cost in introducing such a clearly meta-gaming rule, and when there's a cost, you better make sure you're getting what you pay for.
Now, Chad Underkoffler challenged me to say how you handle Zorro, Inigo Montoya and Batman without Mook rules, and I think those are GREAT examples of other ways to think of th e problem.
First, Batman's an oddball because there's some question of which batman you're talking about. Grant Morrison writing JLA Batman could fight a million ninjas and win but he wouldn't have too because he's ALREADY BEATEN THEM, but that's the extreme case. Going with something like the Animated series, Batman can take on 3 or 4 thugs at once, but he'll have a hard time of it. With that in mind, the only time he ends up in that kind of fight is when he's the one getting ambushed. If he's in control of the fight, he isolates enemies and takes them down one at a time (something easily handled by rules that handle difference in skill + surprise). If he's outnumbered, he'll try to break the fight up so he's taking on few people at a time.
Zorro follows almost exactly the same pattern (and, in fact, has the same question - lots of Zorros out there) which is no surprise given the connection between Batman and Zorro. The main difference is one of flash - Zorro may face large numbers of opponents, but a lot of the whole swashbuckling, umping around, swinging on things and so on is that it keeps him from ever being in one place where he has to fight them all at once. The exceptions to this tend to be the cheesiest, lamest of fight sequences (such as when Zorro, surrounded by men with drawn blades, sings his blade in a wide arc, hitting all their swords and - by some dark magic - knocking all his opponents back.)
Inigo is the most interesting case. He can explicitly take on 10 guys (Maybe 20 - it's been a while) because he's just that awesome, though we could only guess what that would look like. The problem is, it's clear he really sees that as a stretch - this is something that's really freaking hard, possible only because of his awesome level of skill. He's not casually dismissing the guards. Now, this doesn't rule out mook rules - you could do it with mooks that are reasonably dangerous - but it doesn't necessitate them. The same logic that we've applied to Zorro probably is equally applicable here.
Now, this does reveal something interesting - in all of these examples we're really talking less about the actual fight and more about controlling the situation. It's a somewhat different focus, and one that not all games necessarily support, but I think it's a powerful perspective.