My understanding is that there are no standardized personality tests with strong evidence of validity. Using a standardized test might not have any statistical advantages over your own judgement.
ADDENDUM:
If you're just looking to avoid fights, ask people to note down their top ten bands, politicians, and books, and solve for minimum neighbor distance. Then put all the single people together and all it a day.
Does anyone know of a freely available, short personality test that would be appropriate for estimating pairwise compatibility for wedding seating?