My more recent purchases aren't completely business related, yet they dramatically impact my ability to do my business. For one, I purchased a SunBox Desk Lamp for my office. I have a pretty wicked case of Seasonal Effective Disorder which can render me useless if unchecked, and having the little box of light right next to my desk makes it easier for me to get light therapy, and therefore I'm more productive. I also got a footrest, which is making it much more comfortable to be at my desk. Hence, more productive.
The most major purchase (or rather, purchases) I've made recently has been entirely un-business related, but has produced dramatic results in my overall well-being (and - you guessed it - productivity). I decided to cancel my organic produce delivery service (as the veggies were always a bit suspect, and I didn't like them very much), and have made a habit of visiting a farm about 7 miles from my house every Saturday with my boyfriend to pick out whatever fresh produce looks good. Since I started this trend, I find that my mood has improved drastically, I have more energy and feel better overall, and I'm far less likely to settle for junk or pizza because I don't want to eat what's in the house. It's made such a difference, and this is probably the one I'm most happy about, along with a Jivamukti Yoga DVD that I do every other day.
The way I see it, if you are your business, you have no excuse not to keep yourself healthy and well - and those purchases are just as important as the more obviously business-related ones.