This may seem trivial and not even worth mentioning, but I think it is important. Your performance is related to how comfortable you are with your tools. Even if you spend most of your time on the computer, a good writing instrument is a necessary tool for getting work done.
Since you have to use a pen, you might as well get one that you like. This doesn’t mean you have to go out and buy a $50 ink pen (especially if you tend to lose them), but put a little thought into getting pens that you actually enjoy using. It is a small thing, but the happier you are, the better your productivity.