P 38's are great, another option is to get a Swiss Army knife with a can opener. Most of the fairly basic models have them.
Perhaps, however, a model with the can opener (like a climber) usually weighs more (60 Gr) than a SAK classic (14 grams) + a P-38 (I have no idea but nowhere near 45 grams)
Plus if you're like me and were never in the service so you ain't nostalgic about it you can remove the p-38 from your pack after the 5th trip you take it for a ride on your back and don't open any cans. You can't do that if it's part of your knife
Yes it's only a little thing but the decision I'm talking about above is an ounce and a half, with no real loss in utility if you aren't dragging tins of ravioli with you. 10 of these such decisions is a pound of packweight.