The Mini Vivi Nova was the one purchase that totally upped my vape game. I no longer had to carry around a bottle with me - just filler up and go. No need to drip and drive too. Even though I have lots of new gear now, that Vivi stays in my car attached to an Ego Twist so I don't have to pull out my mod from my pocket while driving. I have extra heads in my emergency bag in the trunk.
Edit: I'd say the above was my "latest" game changer. Way back I was using those cigarette like thingys that light up and didn't quite work to well. When I purchased my Prodigy V3 from Puresmoker, I actually quit the ciggys that day. Topped it with a 2.8 ohm atomizer at 6 volts or so with stacked CR123s. That was 2010 so I'm going on 4 yrs. smoke free.
Here she is next to the Icon which I purchased soon after:
