Nanoweb Custom Light Phosphor : Probably the best acoustic strings there is.

These strings work just great for me. After years of experimenting with various brands, I always come back to Elixir. For the acoustic guitar it's definitely the best option - strings stay fresh and "sparkly" for a longer time, even if playing regularly, and the protective cover they put on the strings somehow feels very comfortable. When using a fast-fret for cleaning, these strings retain the "just changed" feeling for at least some weeks. I also enjoy the phosphor bronze string sound - it's a bit more "mid-rangey" than bright in the upper end, but IMO that's the sound an acoustic guitar should aim for anyway.

Only con would be the price - Elixir costs almost twice as much as some other OK acoustic strings, but since they also last twice as long, it's worth it, although, when on a budget, it makes a difference.