Besides the reasons that KK mentioned above about Mundy's understated achievements on the field I've also witnessed his quiet, calm nature and kindness off the field.
I was teaching in a primary school down south when Freo did their pre season community camp down a our way a number of years ago. For those that don't know, players are allocated to nearby schools to talk to children about believing in yourselves, goal setting, perseverance, resilience, etc and then sign autographs at the end.
Mundy, Clancee Pearce & Jessie Crichton came to our school. Mundy spoke in the same way as he plays-minimum of fuss but gave positive messages.
When it came to autograph time he was surrounded by kids wanting anything and everything signed. He was polite to them all, telling them to wait their turn and he'd get to them. I was doing a sort of crowd control thing at the front when he noticed a boy in my class who had cerebral palsy and was in in a wheelchair and waiting at the back with his Mum. Mundy quietly asked the children to wait a minute while he got young Tom to the front. To see this young sports loving boy's face light up while David made a fuss of him bought a tear to my eye. In fact it is again now.
He probably wouldn't even remember this happening but I'd love to meet him sometime to remind him and thank him again. So I'm obviously biased but I think David Mundy is a legend of Freo.