If you are using it as Desktop [ Personal computing ], you can go with any of the distribution based on Debian, which actually pretty good for personal computing. You first need to understand that as you are not using it to provide any kind of service to outside world, Just lock down/disable the services with you filtering device/application, say IPTables to deny all inbound [initialisations] communications, because there is no reason someone is trying to connect your PC as you are not providing any kind of service to other. Set up a AppArmor/SE-Linux for your applications. And yes, don't get SE'd. :b
Obviously, for being a attacking computer, you need different set of tools, which you can easily get for you distribution. BT comes down with plenty of security/pen-testing tools pre installed. But, most of them are multi tools for a single purpose. However, you just need to get a decent tools and install on you distribution if you really need them.
The thing is, when you opt for securing something, you must always have back-up/recovery plan set before attempting anything like this. When you want to play around with your OS, make sure you don't endup with losing your important data.
So, its actually depends upon you to configure you distribution according your specific needs.
Certified: RHCSA, RHCE, CCNA.
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