Just reading about air purifiers and wondering what other things like this I completely missed in my life.
Personal recommendations: kindle, rice cooker.
Edit: It's so obvious to me now (and to most people I guess) that I forgot about my washer dryer. To other young adults reading this, if you can afford it and have the space in your apartment, just get a washer dryer ASAP. Even if you live 5 minutes away from a self-service laundry. It'll actually change your life.