Fuji 23mm f1.4

The Fuji 23mm f1.4 is a workhorse lens.  If you had to purchase just one lens, this would probably be it.  It is great for landscapes as well as portraits.  It preforms well in low light and is quick to focus.

The 23mm f1.4 paired with the Fuji 56mm f1.2 makes an excellent travel/portrait combination.