We have a pretty kick ass trailer, a 2013 PJ trailer that has to be one of my favorite things,  Unfortunately the area I live is anti gun so there is major crime.  I needed a solution to keep the trailer secured.  While no trailer security lock is going to prevent a determined thief they can slow down and deter thieves.  On the best options I have found so far is the Trimax TL75, it does 2 jobs, locks the wheel and acts a chock to prevent the trailer from rolling.

I had a Gorilla lock on the tongue and literally just snapped off one day.  The TCL75 is solid, it goes on and off easily, has a cap to protect the lock from the elements and has a rubber coating to prevent marring your wheels. The lock can used for more than just trailers, you can put it on anything with a wheel including atvs.  They have a smaller TCL65, check out Trimaxlocks.com for their application guide to see which one fits your needs the best.  Get the TCL75 on Amazon for under $50.  I really fell better leaving my trailer unattended now with this device.