I really like my Makita 18V impact driver and drill set. Well worth the money. We used Milwaukee, dewalt and Makita when I built my deck. (when my tools were stolen, I went to Makita to replace my Dewalts and am very happy.) Agree with the Bo wrench - it works nicely. You will also need a random orbit sander. I have a Rigid but also like the Makita. That being said, Makita, Milwakee 18V and Dewalt 18V tools are very good. Stick with one of those brands.

A Wonderbar is great for demo, and can be used to space out/bend in boards as well, in conjunction with the Bowrench.

Have you got joist hangers and hurricane ties on your framing structure? If not, I love the Bostich metal connector nailer.

It might be useful to know what tools you have now.

For the average homeowner something like a metal connector nailer is a pretty specialized tool. While quite useful, it's not likely something you'll be using a lot after your deck is completed. You might want to check eBay, Craigslist, local pawn shops, etc. for used ones.

I've bought all of my nailers used on ebay. You can resell once you're done with your deck if you don't think you'll need them on future projects.