Fiddler rocks. Fiddler is a free web debugging proxy for any browser, system or platform. I’ve only ever used it on Windows so I can’t speak to how it performs on any other OS, but on Windows it’s pretty great.
A lot of why I like Fiddler so much is just personal preference. The network tab in Chrome dev tools does a lot of the things I use Fiddler for, but I like Fiddler’s interface better. Fiddler does have some differences, though. If you want to save a few rounds of requests across page refreshes so you can compare them to each other, Fiddler lets you do that. It also has a more powerful filtering system than Chrome dev tools, so you only have to see the requests you care about.
Another awesome thing you can do with Fiddler is set up a mobile device to use it as a proxy. Logging from a mobile app is all well and good, but sometimes it takes much longer to add logging, rebuild, and redeploy than it does to just update your mobile network settings to use Fiddler as a proxy.
While I mostly use Fiddler for very simple request/response viewing, you can do some pretty cool stuff with it like performance testing, session manipulation, and security testing. There are also lots of add-ons you can try if Fiddler doesn’t already do what you want, plus you can customize it on your own.
As much as I love Fiddler, there is one caveat I need to mention. Firefox is totally incapable of coping with Fiddler unless you change some settings. I strongly recommend that you do that immediately if you install Fiddler because you will forget that you have Fiddler running, try to test something in Firefox, and freak out because everything is suddenly broken (not that I’ve ever done that. Repeatedly). It’s not, Firefox should just be ashamed of itself. Even IE can handle a freaking proxy. You used to be cool, FF. Now you’re like a broken down racecar that’s getting lapped by a go-kart. With square wheels. That’s been set on fire.
Why should you care about Fiddler? It might be better than what you’re doing right now. Having better tools to do the tedious stuff for you means more time for actual development, even if you have to invest a few minutes up front to figure out if Fiddler is actually better than what you’re using right now. It won’t magically make you a better developer, but it will give you more time for development, which can be pretty close to the same thing :)