This thread deader than my soul in JC. Like most of my life, reviving it is probably a mistake.
Blastoise @ Icium Z 
Ability: Torrent  
EVs: 252 HP / 252 Def / 4 Spe  
Bold Nature  
IVs: 0 Atk  
- Scald  
- Blizzard
- Rapid Spin  
- Toxic / Refresh
0 SpA Blastoise Subzero Slammer (185 BP) vs. 0 HP / 0 SpD Sceptile: 266-314 (94.6 - 111.7%) -- 68.8% chance to OHKO
Not a good lure, but it does lure Sceptile in. Guarantees a KO after Rocks but you lose a slot for Toxic/Refresh.
Slowking @ Assault Vest  
Ability: Regenerator  
EVs: 212 HP / 252 SpA / 44 Spe  
Modest Nature  
IVs: 0 Atk  
- Scald  
- Fire Blast  
- Future Sight  
- Grass Knot
252+ SpA Slowking Fire Blast vs. 0 HP / 0 SpD Sceptile: 252-298 (89.6 - 106%) -- 37.5% chance to OHKO 
252 SpA Life Orb Sceptile Leaf Storm vs. 212 HP / 0 SpD Assault Vest Slowking: 291-346 (75.7 - 90.1%) -- guaranteed 2HKO 
For if you're feeling ballsy enough to stay in.
Seismitoad @ Poisonium Z / Life Orb
Ability: Swift Swim  
EVs: 252 SpA / 4 SpD / 252 Spe  
Modest Nature  
IVs: 0 Atk  
- Rain Dance  
- Hydro Pump  
- Earth Power  
- Sludge Wave
252+ SpA Life Orb Seismitoad Sludge Wave vs. 0 HP / 0 SpD Sceptile: 255-302 (90.7 - 107.4%) -- 43.8% chance to OHKO 
Toad is either weak or Sceptile is deceptively bulky. Adamant Max Attack Life Orb Poison Jab OHKOs though.
Vaporeon @ Icium Z  
Ability: Water Absorb  
EVs: 252 HP / 252 Def / 4 SpA  
Bold Nature  
IVs: 0 Atk  
- Scald  
- Ice Beam  
- Wish  
- Protect
0 SpA Vaporeon Subzero Slammer (175 BP) vs. 0 HP / 0 SpD Sceptile: 312-368 (111 - 130.9%) -- guaranteed OHKO
0 SpA Vaporeon Ice Beam vs. 0 HP / 0 SpD Sceptile: 160-190 (56.9 - 67.6%) -- guaranteed 2HKO
Beats other Grass types that think they can wall you as well (like all the above sets).
Palossand @ Colbur Berry  
Ability: Water Compaction  
EVs: 252 HP / 252 Def / 4 SpD  
Bold Nature  
IVs: 0 Atk  
- Stealth Rock  
- Shadow Ball  
- Sludge Bomb  
- Shore Up
0 SpA Palossand Sludge Bomb vs. 0 HP / 0 SpD Sceptile: 148-176 (52.6 - 62.6%) -- guaranteed 2HKO 
Finally not a Water type. Has the added benefit of being able to poison.
Sceptile isn't coming in on anything that isn't a bulky water/ground so apologies for the uncreative sets.