OK, first of all, just a little friendly advice, not trying to tell you what to do or anything, but please don't double post, people will get to your thread eventually, you just posted this topic an hour ago. Double-posting is against the rules here at SPPf, so the mods don't like to see it.
Special Attacking Lapras (Water Absorb)
Ice Beam
Thunderbolt/Confuse Ray
Surf
Rest/Confuse Ray/Sheer Cold/Psychic
@Leftovers.
OHKO Lapras (Water Absorb)
Horn Drill
Sheer Cold
Sleep Talk
Rest
@Leftovers.
Physical Attacking Lapras (Water Absorb)
Body Slam
HP Ground/Ghost/Rock
Curse/Dragon Dance
Rest/Ice Beam
@Leftovers.
Since your Lapras has a neutral personality, it doesn't really matter which moveset that you use. The OHKO set really isn't useful in-game though, and you would want a defense/special defense raising personality for it. I would use the special attacking moveset that I listed, or something similar to it. Lapras' maximum attack and special attack stats are actually the same, so the only real disadvantage of the physical moveset is that you won't get STAB, plus Lapras doesn't get as good of a physical moveset as it does a special moveset. Unless this Lapras is purely in-game, then I seriously recommend getting one with a good stat enhancing personality, and EV training it.