Air is great for fast travel and scouting, has fair combat abilities and when paired with offense or utility, can be a nice surprise build. Water has some great forms but some of the upper level forms are weaker than offense, utility, or defense forms and are still tied to water only. However, they do have advantages of swimto when the opponent isn't indoors and surprising opponents traveling or learning in the water and some of the forms are absolutely beastly and have the added bonus of allowing some degree of under water exploration. Defense usually means easy ranking and if you end up with some regen form to back up your others, you can take down almost any NPC in the game, given enough time. There are really just too many variations and combinations of shapefocus that it's hard to narrow it down and even picking categories doesn't mean that you’ll end up with what you envisioned to begin with.