Messanna - egwene for sure, though it would be pretty cool if the black ajah hunters (pevara, et al) managed to do it since almost all of their work was for naught.

Moridin - rand. it has to be, whether as a gesture of mercy or in a pitched battle, rand.

Cyndane - hmmm, i think this could be anyone from alivia to moraine to elayne or aviendha or even accidental death from mindtrap shattering. or even the 'fins. i'll go with moraine though, she deserves another big kill.

Moghedien - nynaeve = poetic justice, but so does birgitte. maybe a young gaidal cain turns up and does the job?

Demandred - love the mat theory. out-general this you dumb fcuk. you just became the third best.

Aran'gar - narishma. has to be a male channeler for sure...

Here are a couple more bad guys to throw in for fun:

Taim - logain. derr.

Shadar Haran - hmmm. the fain theory is good, but i also like the idea of someone like rhuarc doing the deed here (as in a smaller character, but highly nobel and talented fighter being rewarded for his awesomeness). so i say rhuarc.

Gholam - mat or elayne if she figures out how to duplicate the effects of the foxhead.

Slayer - i go with lan here. yeah, i know perrin has great reason to, but i love the idea of lan confronting this s.o.b.

Padan Fain - hmm, maybe lan here instead? maybe shaidar haran? i am not feeling rand killing him, he has too much else to do, but it is a definite possibility.