I really like going through water or even dry through a J-hook. You lose a little flavor with more percolation but it's so smooth. It's good to have the option so I have a WPA for nearly every device I own
I want to highlight this because it's happened a few times. If the Tinymight really didn't care about after sales support they wouldn't be tossing in freebies like this. This lends to the argument that they're drowning in demand.
Go with the VTC6 as a minimum. It's a good cell, and the device was build around it so it's always a safe bet. The HG2 or 30Q should work in theory but like
@LabPong said he had issues with the 30Q and the HG2 is an older cell that may not keep up with the demands put on the battery from the programming of the Tinymight. Any of the recommended unregulated cells from the link I posted earlier like the 26A, VTC5A, VTC5D, 20S, 25R earlier should work as well you'll just lose out on some capacity. I'm big on Molicel not just because it's the top pick from that list but also the attitude of the company towards users like us. When I placed my last battery order I grabbed a couple extra VTC6's to use exclusively in my Tinymight as well as ten 26A's that I'm using in my Mi2, Mi3, Tetra P80 (just arrived!), FW7 (incoming), LV Paranormal 250C, Tera V3 and future Nomad 2. I keep one pair married for the dual cell devices.
Once demand dies down and/or they expand their operations to keep up I wouldn't mind a dual battery Tinymight. It's not on my wish list and I'd want to see the current Tinymight refined first (to fix its quibbles) but there's probably a demand so hey why not right?