I'm about to get my first two this year, as soon as I can afford it. I've been thinking long and hard about what and why, and they're both small. upper back and foot.
I tend to not like the huge memorials, complete with dates of death and names. I don't get why you'd want the date that someone you loved died inked permanently on your body.

As for ones I like, my uncle has a DNA strand around his arm, and my riding instructor has a pair of feathery blue wings on her back. Her training service is called Blue Feather Farms.