I've used several different slugs. I like the Remington Accutips in both 12 and 20 gauges: 12 for elk, and 20 for deer. I'll see if I can find a 12 gauge Accutip that I recovered from an elk and share a photo: Remington should pay me for it to use in their ads because of perfect expansion.
Second this vote for accutips.
In 12 ga they go right through, leaving a solid blood trail, and still have plenty of energy to put holes in trees.
That one was a blacktail at 85 yards.