Excellent list Br UBAB but I'll throw a curve ball and suggest the most important one of these is actually #11 and not #1.
It's funny how that one is tucked away right in the middle.
As for its hadith, I would go fo the Hadith Qudsi which says that a believer draws closer to Allah by performing obligatory duties and then nearer still by performing voluntary duties.
I bought a poster of this over 10 years ago for every one of my coworkers back then
What was their reaction out of interest?
Thank you Br. Khalid for the lead for #11... their reaction was great - we were in the middle of a major pharmaceutical manufacturing expansion project at that time which meant many, many long hours. My co-workers were part of an engineering and construction team that came from all over the world so I got to meet many great people and basically had to grow up very quickly, as I was the youngest member of the team.
The top five suggestion they agreed with were as folllows:
#1 was the most important in their opinion, then #2, 17, 18 with the men on the team rounding out with #19 and ladies with #21.
It was an interesting mix of people - we probably would have never met in the outside world. What was nice was that the older men and women treated me like their son, as many of them chose not to have children, so they would always give me (good) advise and looked out for me. I was young, so didn't do much dawah, but got them hooked on halal hakka-chinese food, which they really enjoyed.