Well, if Magcargo is going to be here, want to put a set I was decimated by (OHKO my favorite Clefable and you get my attention) but have been trying to figure the best way to work it.....
Kabutops (M) @ Liechi Berry
Ability: Weak Armor
EVs: 252 Atk / 4 Def / 252 Spd
Adamant Nature
- Aqua Jet
- Rock Slide / Stone Edge
- Flail
- Endure
With being attacked on switch in, Weak Armor will activate. You will now be faster than the opposing Talonflame. The damage does not matter because nothing will OHKO you and you will be spending time at low HP. From here, it gets tricky. If the Talonflame has damage already, you're free to kill it with your Aqua Jet. If not, you will want to Endure. Endure is a +3 so Gale Wings is no issue. A switch (likely a U-turn, which gives another speed boost) is good as you are likely to outspeed what they have (unless a Scarfer and no U-turn). Endure can be used every second turn (Protect rules) and gives you a chance to survive something and possibly get another boost. The set is meant to ruin a number of expected counters (discussion for another time) and then kill Talonflame upon return (the most likely next switch unless they have a Bullet Puncher instead).
If no switch, the Berry will
almost be the boost required. OHKO is possible... but 19% chance of. Could go Band, but same result and choiced. Weakness Policy is an overall viable option (especially for ruining physical fighters who try and take this thing), but will not help for Talonflame. Waterfall will 2HKO, but no priority and Rock Slide exists. Flail is meant mainly for things after Talonflame, but can potentially OHKO (guaranteed if using Berry).
Another option you can do is to shift all the speed EVs to Defense to survive 2 Life Orb BBs (yes, you need all 252 to avoid 2HKO after Weak Armor) but that requires a second activation of Weak Armor to outspeed Talonflame and is not recommended. It cannot avoid 2HKO if they are Banded instead. In the case of being burned on the switch, you can still OHKO with Rock Slide (or Edge) on next attack, but they will probably flee.
Soooo....
For those who want a true counter, 20 EVs for Defense will ensure Banded BB will not 2HKO.
Kabutops (M) @ Life Orb
Ability: Battle Armor
EVs: 252 Atk / 20 Def / 232 Spd
Adamant Nature
- Waterfall
- Rock Slide / Stone Edge
- Earthquake
- Rock Polish / Knock Off / Aqua Jet
Switch in, survive, Rock move, kill. Simple. After that, you will unfortunately be underspeed to deal with other BS commons, but you'll have coverage. The EdgeQuake combo is a given, the last spot is if you prefer STAB priority, item killing, or being able to outspeed things without needing rain support.