Top 5..or 10... MUST haves for a reef tank

[kam]

Hey guys,

Ive had my tank up and running for 3-4 years now but was just running a FOWLR tank. Im getting back into the reef hobby and am finding out that all my old knowledge is starting to get... old!

I thought it would be a good idea to start a thread for people with limited knowledge to let them know what the Top 5 (or 10) key products are to help ensure a healthy Reef tank.

What, so your own words or list, what would be the top 5 (or 10) things you'd recommend for a Reef tank?? (skimmer... lights... etc)