I like Horsechopper: Trip, Reach, 1d10. I also like Halberd. Trip, Piercing, Brace, Slashing, and 1d10.
I like the Phalanx Soldier Archetype. You can fight with Pole Arm and Shield, but there is a Feat whose name I can't remember that also lets you fight Pole Arm and Shield.
I like the Eldritch Guardian Archetype for a Tripping character. You get a Familiar that knows all the Combat Feats you know, including those Teamwork Feats that are also Combat Feats. So you can take Coordinated Maneuvers that gives you +2 on all your Combat Maneuver Checks. You can take Harder they Fall, which will let you Trip creatures that are otherwise too big to Trip, and you can take Paired Opportunist which means that if either you or your Familiar get an Attack of Opportunity, you both do.
I normally don't favor Pole Arms as Trip Weapons. To my mind, the best thing about a Trip Weapon is that in the event of a catastrphic Trip Roll, you can elect to drop your weapon instead of getting Tripped yourself, but you will miss your Halberd when it's gone. But if a bad roll makes you drop your Sickle, you just shrug your shoulders and pull another one off your belt. Another Trip Weapon I've been fascinated by is the Throwing Shield. If you acquire a Blinkback Belt, you get it back automatically. Your Throwing Shield could also be a Quickdraw Shield, letting you re-draw it as a Free Action, so you could Trip someone at Range, get your Shield back then make your Attack of Opportunity with your Throwing Shield again. That would be very Feat-hungry, requiring you to take Snap Shot Feats which would require you to take other Feats, but it seems really cool.
