Other than the stuff that I'd consider "regular" on an OSX install,
Flash
WMV
Quicktime
Ilife/iwork plugins
The only *other* plugins I run on Safari are:
Divx webplayer
1Password
That's it. Nothing too kooky or weird, and one of those only comes into play on a small number of sites I visit.
Despite that, I get beachballs. All the damn time. It's absolutely infuriating, that I sometimes have to wait upto 10 seconds to click a link that Firefox would have ready straight away.
Firefox crashes. In fact it crashes more than safari (safari has only crashed twice compared to ffox's 15 or so in my current experience on SL). But when it crashes, I can be back up and browsing, tabs restored, in a couple of seconds. Meanwhile, Safari keeps beachballing.
I want to love safari. I really do. I miss not having full services and scripts capabilities with Devonthink and the like when I'm on FF. But Firefox works. It might be a tad slower than Safari, especially when you're dealing with javascript heavy sites like gmail, but it doesn't beachball. It doesn't lock up. It crashes occasionally, but then its right up again and ready to go, and has at least given me feedback on which site caused it to crash!. There's nothing left for Safari anymore. Once Mozilla work in full services support I'll never even consider going back. What's there to miss. Webkit is faster, but the rendering engine's speed is a complete second fiddle to the browser's stability. Safari used to be much prettier than FFox, but
http://www.takebacktheweb.org means that Firefox can be far better looking, in so many different ways too, than Safari. There's no reason to use it at all.
/rage