Veni, vidi, VICI!!!
What do you think? If Kakashi was to combine Raikiri with 1000 Years of Pain, it would be a super deadly Jutsu. It would bust a hole through the opponents butt!
It would be VERY disgusting, though...
Excuse me, but Raikiri isn't about tricking the enemy about using the tiger seal. It's about hitting the enemy in his blind spot, or , to be specific,I suppose it could work, but the whole point of the 1000 Years of Pain jutsu is to trick the opponent into thinking that you are actually going to use a jutsu with the tiger seal. Besides the Raikiri would probably be evident before use and may be able to be dodged. It really depends on the opponent, but it would hurt.