I'm going to throw in another vote for HA or SSV. HA is super versatile, but the draw can get a little tough. The draw on the SSV is super easy, but not as versatile. I too have my HA hooked up to a bong to water cool it and it gives huge rips. The Solo looks like a sick portable vape that I am considering, but from what I've heard, the draw is very hard (like drinking a frozen milkshake). Also remember that you cannot use the solo while it's charging unless you buy a $40 aftermarket adapter.