the kitchen and the bathroom!
Some tips to remember:
~ Don't over improve, pick materials that focus on functional space and a little of the "wow" factor. Sometimes a buyer might have different taste and end up renovating again so it's probably wise not to over spend on materials.
~ Keep colors neutral
~ Safety features: GFCI (ground, fault, circuit interrupter)
~ Ease: Remove walls if need be for better access, work on the floor plan to make things more functional. When choosing appliances and features pick things that are easy to use and easy to clean.