Human Urine: Many swear by this. Perhaps it IS diet related or species of deer or presence or lack of humans that explains why it works for some and not others. Note: application would likely need to be "regular" and for sure after a rain.
Dog Hair: Many swear by this. Again, could be species type (of deer) or type of dog, or the issue of fur collected that is "too" clean that explains the successes vs the failures.
Cougar/Predator Urine: as a deterrent this does have mixed results, my guess, if it is an area without cougar, the deer would not "know" to fear it.
For me, this is a "no go" as I have to question the ethics regarding predator urine collection. Are the predators kept "caged and catheterized" to collect from live animals? Frankly I cannot see enough of these animals hunted and their urine collected by hunters and "sold" to the sellers; so just HOW is this substance collected? Plus it is pricey, and must be reapplied regularly.
Mothballs: my concern here is toxicity to livestock, pets, wildlife, and unsuspecting children. For me this is a "no go" due to safety concerns.
Commercial Deterrent Sprays: the issue here is two fold, expensive and effectiveness. I have tried pretty much all the sprays for detering raccoons (placed Fruit Loop cereal in Tupperware, heavily sprayed, allowed to dry, sprayed again) zero success - container opened, Fruit Loops gone.
Most of these commercial sprays "claim" multiple species, including deer, but based on my raccoon trials, I doubt their efficacy; plus they are pricey and must be reapplied regularly.
Electric Fencing: Can be effective, assuming it is placed appropriately; it will only "shock" them if their nose or tongue hits a live wire. I suspect in many cases it is the "visual barrier the fencing creates that is more often the actual deterrent.
Barrier: Basically it is not the strength of the fencing but it's visual presence. Bird netting on bamboo or junk poles is highly effective as are "flagged" strands of fishing line. The key is an absolute minimum of 8 feet; 10 or more if you have heavy snow load, a slope or extra large deer.
If the minimum 8 ft height is not an option you need to widen the "fence" or slope the fence. Two six foot fences placed 4-6 ft apart or three 4 ft fences, 2 ft apart, OR two fences with
trellis or board or flagged line to a width they cannot jump - MUST be visible! A great solution is to use the space between the two fences as a poultry, duck or dog run.
Flagging: this could be actual flagging tape, mylar strips, foil strips, old cD's or computer discs, yarn, cloth strips...the key is that they flutter/move in the breeze; the movement unnerves the deer; flashing from reflective items works best, long (8-12 inch) and colorful, second best. Suspended bars of "Irish Spring
soap or dog hair are also said to work. This also makes a low visibility barrier such as fishing line visible.
Junk Pole Fencing: this can be time consuming, but VERY cost effective (search the permies site for how to instructions). Essentially you use saplings or other "junk" to create a palisade type fence with two horizontal poles attached to verticals, lay in the junk poles upright and hold in place with two more horizontal poles, rope, mesh etc. This will NOT keep out climbers or diggers, only deer.
Deer proofing can initially be time consuming and/or expensive; but always factor in the cost of doing it "right and doing it once" before opting for a cheap or easy solution that fails.