Luxury vinyl flooring, including luxury vinyl plank and tile, is one of the quickest and cleanest types of flooring to install. The floor's click-and-lock technology makes installing it over an existing subfloor easy. New luxury vinyl flooring is a type of floating floor.
You can't go wrong with oak, maple, or cherry flooring. Bamboo (technically a grass), walnut, ash, and mahogany are more examples. Wood from rarer and more expensive trees, such as teak, jarrah, and mesquite, will cost you more.
Screws are again the best option if you need to run conduit for electrical and plumbing systems underneath the floor. Screws have the additional benefit of holding the boards in place without ever coming loose, which is far more preferable to using nails. Screws are the better long-term answer because of the tighter grip they provide.