When developing Web apps you spend a lot of time in the browser, and before long you have a crap-ton of open tabs which slows the system down and is a total pain to navigate around in.
Someone on Twitter mentioned Paw being awesome - and boy were they right!
Paw is packed full of useful features like HTTP header auto completion, response formatting with syntax highlighting and the most useful of them all: Request grouping. Paw will sort your requests by host and HTTP method2 making it really easy to find the request you looking for in a snap.
Having an easy way to edit and execute complex HTTP requests is super awesome and saves me a lot of time. Paw can also generate code for your request, but alas no perl.
Paw comes with a selection of HTTP libraries, each of which as some shortcomings3 - the default is called "GCD AsyncSocket" provides more debugging options but is less battle-tested than the other options provided4.
I highly recommend Paw.