Panzer Clone

Either made by Infinite or Shenxi.
Panzers are Recessed Bottom Buttons which are much less "worrisome" and cumbersome to use than an exposed Bottom Button such as the Stingrays (although an Infinite Stingray Clone is a great Tube Mech for what they are).
If not a Panzer then any other such with Recessed Button and Locking Ring Design (IMO).
Just be careful on what Battery you use in them or any Single Battery Mech depending on what you plan to strap on top of it. Make sure it can handle the draw and demands of your Build.
Plenty of Battery Threads to research to be sure the "True Specs" will match well and safely with your Atty/Build.
Sony VTC4, LG HE2/HE4 or HG2 are great choices and proven safe by the Resident Batt Experts here on ECF. Be sure to procure from a proven and reputable Source as there are tons of Fakes and Charlatans out there on the interwebz AND at B&M's too.
Can't go wrong with Batteries from RTDVapor
Batteries - Sony,LG,Panasonic,Samsung..... - RTD vapor
Mechs are AWESOME and with a little bit of research, education, and due diligence they are quite safe and easy to use. I mainly TC Vape (3 different Devices) nowadays but did hang on to 1 from my Mech Warrior days (a Hollowpoint Mech Box Mod by Silver Wolf Customs) for those times when the fancy strikes. Matter of fact,,,, Football Day and it will be raining so time to reactivate that Soldier, strap a 13/9 RDA with a dual-coil build at approx. 0.22 R, and enjoy some steam-rolling Mech Dripping Vaping today myself
Whatever you decide, Enjoy & Vape On!