I know 3.5 had a slew of ways to increase reach, however in PF I've only found a couple. I'll be playing a tank build and would like as many ways to do this as possible. I know of the Lunge and Monkey Lunge feats, the Enlarge Person spell, reach weapons of course, and being a larger size category, but I can't seem to find anything else.
Approved material is any Paizo and most Dreamscarred Press (though DSP material still has to be run by the GM). 3.5 and other 3pp material is unlikely to be approved but it's not autobanned so if something increases reach but seems reasonably balanced it might be approved.
I will be playing an Oggr (Dreamscarred Press, Bloodforge) and my class is Inquisitor gestalted with a version of Sephyrus that has been approved with tweaks.
NOTE: Increasing threatened area is not increasing reach, though I do plan to take Combat Patrol and related feats as well.
Update: Still interested in answers to this with the above build or with the updated build. Updated build is a Half-Giant Sephyrus + Warder (Zweihander Sentinel) and I will likely take the first level in both Telekinetic Weaponmaster and Living Monolith later.
Best Answer
One highly effective method of increasing reach in Pathfinder, not yet mentioned, is the Cleric Subdomain Plant(Growth). This option is different from, and superior to, many other methods of increasing reach in Pathfinder. This domain option provides more than just Swift Action Enlarge Person. It also provides the character with tactically valuable on-demand extra 5' steps.
Using the enlarge ability also provides the user with free virtual 5' steps!
I've played a Plant(Growth) Cleric in Pathfinder through 10 levels and can testify that it is extremely effective. In terms of reach, large size stacks with longarm. A Large biped wielding a reach weapon and buffed with longarm will have 25' reach and a ridiculous 60' diameter threat circle. The enlarge ability allows one to walk around normal-size yet swiftly become large if combat occurs.
The best part is the free virtual 5' step that comes from frequent starting and stopping of enlarge person. This is a tactical move that will make you smile every time you use it.
Getting Large: Your unbuffed longspear-armed PC can threaten 30' away with just a 5' step. Take a 5' step toward the foe, then swift Action enlarge person and choose to grow toward the foe. You now threaten the foe 20' away and still have your normal actions. It's as if you got an extra 5' step.
Getting Medium: Foes will quite reasonably feel threatened by the spear-wielding giant and may try to run in close en masse. Say foes survive your Attacks of Opportunity and move adjacent to you. When your turn comes around the first thing that happens is that enlarge person ends. Choose to shrink away from your attackers. They are no longer adjacent. It's as if you got an extra 5' step.
You can even 5' step away and swift enlarge person again, choosing to grow away, which leaves large you threatening foes who are now 15' away. You may full attack or safely cast a spell, yet foes will draw more AoOs if they want to close with you again. This works exceptionally well for area denial builds using a reach weapon. You can prevent foes from landing a Full Attack, yet you can always Full Attack.