Mkay, my take on it:
Lickilicky@ Life Orb
Quiet
34 HP / 224 Atk / 252 Satk
-Hammer Arm / Explosion
-Ice Beam
-Thunderbolt
-Fire Blast
The thing is though, unless you run the Choice Specs, many of the otherwise OHKOs fall short and into 2HKO territory. Observe:
Fire Blast
Metagross(252 Hp, neutral nature) 81.59% - 96.15%
Skarmory(252 Hp, neutral nature) 108.98% - 128.14%
Forretress(252 Hp, neutral nature) 231.64% - 272.60%
Tangrowth(252 Hp, neutral nature) 116.34% - 136.63%
Weezing(252 Hp, neutral nature) 54.49% - 64.07%
Gengar(4 hp, neutral nature) 65.65% - 77.48%
Mismagius(252 Hp, 196 Sp.def, + nature) 30.86% - 36.11%
Dusknoir(252 Hp, 180 Sp.def, neutral nature) 31.29% - 37.07%
Cressilia(252 Hp, 252 Sp.def, + nature) 18.47% - 21.85%
Bronzong(252 Hp, 98 Sp.def, + nature) 59.76% - 70.12%
Metagross is no longer an OHKO (without SR), Cressy and the ghosts are even more impossible to hit, but everything else is still an OHKO or 2HKO.
Thunderbolt
Gyarados(212 Hp, neutral nature) 112.76% - 132.81%
Skarmory(252 Hp, neutral nature) 86.53% - 101.80% Use Fire Blast
Milotic(252 Hp, neutral nature) 45.69% - 53.55%
Slowbro(212 Hp, neutral nature) 67.71% - 79.69%
Slowking(212 HP, 252 Sp.def, + nature) 47.66% - 55.99%
Changes here are that you must now use Fire Blast to guarantee OHKO Skarmory since T-Bolt could fall short. Slowking and Milotic also turn into possible 3HKOs. But overall, still not too bad.
Ice Beam
Salamence(120 Hp, neutral nature) 144.04% - 169.53%
Garchomp(32 Sp.def, neutral nature) 133.61% - 157.14%
Dragonite(252 Hp, neutral nature) 112.18% - 132.12%
Hippowdon(252 Hp, neutral nature) 67.38% - 79.29%
Zapdos(252 Hp, 252 Sp.def, + nature) 43.75% - 51.56%
Cradily(252 Hp, 92 Sp.def, neutral nature) 50.00% - 58.78%
Hippo turns into a 2HKO, Zappy and Cradily into probable 3HKOs. Dragons still die though, which is good.
Hammer Arm
Blissey(148 Hp, 252 Def, + nature) 55.09% - 64.68%
(252 Hp, 252 Def, + nature) 53.08% - 62.32%
Regice(252 Hp, 252 Def, neutral nature) 45.88% - 54.12%
(252 Hp, 252 Def, + nature) 42.03% - 49.45%
Tyranitar(252 Hp, neutral nature) 96.29% - 113.12% (will not OHKO, even with 252 EVs)
Snorlax(220 Hp, 252 Sp.def, neutral nature) 54.65% - 64.34%
Hammer Arm is the clear winner here imo. 2HKO on Snorlax, possible OHKO on T-tar (guaranteed with SR?), 2HKO on Blissey and possibly Regice (with SR) makes this the superior move over Focus Blast.
So overall, I personally think the Life Orb idea is by far more versatile. However, Specs with Hammer Arm and an Atk neutral nature will still yield the same results for Hammer Arm calculations and turn the other 2-3HKOs back into OHKO and 2HKOs for the special attacks.