Web Log Analyzers?

sammy.lost-angel.com asks: "What's the best web log analyzer out there today? It's time to upgrade our horribly out of date one and I'm not sure what's good out there at this time. Our site receives about 50,000 hits a day, so things like remembering what's already been analyzed can save a lot of time." What about log analyzers that can work on more than one type of web server? An analyzer that could parse access data for, say, IIS and Apache would be a nice tool!