Basic layer-
Neptune Armed Zephyr
Dual layer-
Acid Anubis Yell Orbit
God layer-
Nightmare Longinus Destroy
Cho-Z layer-
Archer Hercules 13 Eternal
GT layer-
Master Diabolos Generate
Sparking layer-
Rage Longinus Destroy' 3A
DB layer-
Guilty Longinus Karma Metal Destroy -2
Honorable mentions go to: Kerbeus Central Defense, Xcalibur Force Xtreme, Driger S Heavy Fusion, Deep Chaos 4Flow Bearing, Cho-Z Valkyrie Zenith Evolution, Cho-Z Achilles 00 Dimension, Lord Spriggan Blitz Dimension', Regalia Genesis Hybrid, World Spriggan Unite' 2B, Vanish Fafnir Tapered Kick -3
For explanations:
Neptune is an amazing Classic-era staller, and a viable enough combination in stock. The disk can be improved a bit, but compared to other stock basic layer beys it's an incredibly strong contender that's usable against nearly anything. Xcalibur comes close but lacks a bit of consistency and is often bursty without a ' upgrade, and Kerbeus is a lot more of a one-trick defender that has similar disk issues.
Acid Anubis is in a similar pool like Neptune, with Orbit acting as a pseudo-' driver with massive stamina and Yell supporting it just the same. Out of the Classic legal stock combos this is the most likely one you are to see at the tournament level because it is just that good at surviving without any real modifications needed to it, and no other dual layers really get close to it in stock alone. Lost Longinus is a trap option here. It's a great layer and banned from Classic for good reason, but its stock is rather atrocious and it relied hard on other drivers like Hold to win the LAD game if it couldn't secure the KO.
Nightmare Longinus has quite the aggressive power, plus the LAD to beat down whatever God era stuff it can't tear to pieces. Spriggan Requiem is a trap choice for this slot. Spriggan Requiem may have a better layer, but its stock combo is
terrible on Zeta while Nightmare Longinus is top-tier out of the box (and the same logic applies to Maximum Garuda as well, a powerful layer with a horrendous stock). Deep Chaos gets a mention for almost exclusively having good parts and yet being so risky that it becomes difficult to use them to their full potential in stock.
Archer Hercules, despite the terrible disk, is one of the most functional Cho-Z beys in stock with rather high stamina and LAD. Other beys with stronger layers tend to have cruddy stock combos (as seen in Hell Salamander 12 Operate), or if it's one of the Phoenixes rely on the other to fill it in while also playing way too hard for same-spin (where Friction and Atomic do best). Shout-outs to Cho-Z Valkyrie and Cho-Z Achilles for their late aggression, though Cho-Z Valkyrie was a bit lackluster and it's gimmick was self-defeating enough that it was optimal to launch it soft enough to avoid activating it and Cho-Z Achilles was difficult to control effectively with a tip that wore down too quickly.
Master Diabolos was a true "I can do anything" sort of bey in the GT era. Good same-spin stamina, it could make for an anti-staller or just whale on anyone that got too close to the ridge, and its LAD is serviceable enough on Generate (if a bit of a coin flip). Other powerful layers tended to have weak stock combos like Imperial Dragon (it's way too bursty in stock), Judgement Joker (and it's non-synergizing disk), and Zwei Longinus (with a terrible disk and a driver that lacked the grip it sorely needed). A shout-out to Lord Spriggan for making a decent enough pseudo-Judgement in stock if you could get a same spin match from it (Lord's same-spin is underrated imo), and another to Regalia Genesis which could win nearly any battle if its batteries were in a good state to keep it spinning on the ridge and safe from harm for long enough.
Rage Longinus should be no surprise, Rage was meta with little more than a driver change for a while and Destroy' was still plenty good enough to make its stock a powerhouse. World Spriggan gets a shout-out for also being meta-worthy, but Unite' really needs to be swapped out for something else to make it work. If you really wanted to get into the nitty gritty one could also make shout-outs to beys like Helios Volcano for being such a hard wall to right spin, or either Lucifer for being hard walls to left spin, but they're a bit too matchup dependent for my liking.
And Guilty Longinus, even in the nerfed form that got released, is a strong attacker. Of course you'll wear your teeth down using Metal Destroy so swapping drivers is recommended for longevity reasons, but nobody will deny that Longinus is still as strong a line as ever and early testing is already proving it to be meta-shaping. Vanish Fafnir deserves a little something for being a strong stock combo pre-Guilty despite the awkwardness of Kick, and the same is true of Cyclone Ragnaruk which is basically the king of same-spin in stock assuming you got a decently controllable Never on it plus top-tier LAD to boot (though it suffers slightly from LAD consistency issues and can be bursted). I don't know what to consider Dynamite Belial with the gears on this list, so I'm assuming no gears for now. Not entirely sure all gears is desirable though.
And also a quick honorable mention to Driger S as the most viable remake layer stock combo in the format where that whole combo is legal. The plastic gen remakes with metal are just competitively bad in general, the MFB remakes don't have good combos to support them, and Wolborg might've stood a chance if it didn't have the 8 disk pushing it back into Limited where it's a bit lightweight (but still surprisingly strong admittedly, capable of outspinning stock Hazard Kerbeus from the same set).
Cincinnati-based Organizer, and owner of every single currently released TT Burst bey part in at least one color. Hard to think of anything I don't have from MFB either...