I use straight shaft paddles - one Zaverel carbon, and one Bending Branches as the spare.  The paddles I use are shorter than those I use for tandem - the seat is closer to the water, so need a shorter shafted paddle.  That's for lakes.

for white water, I use a heavy fiberglass Werner Guide model, I think it is, and an Aqua Bound Odyssey as the spare - need something that will take the beating.