Drop-Off Needles: These needles are mainly used in medicating animals but may still be used when you want the syringe to fall out quickly (for Deer and Bison this is a good choice). In a case were the animal could run off into thick cover or if you do not want the animal to run around with a syringe sticking out of it.
Large Collar Needles: Large collars are used mainly in immobilization work. There are a few cases where you may have to use the large collar to give medication, such as (on thin skinned animals where you would be using large quantities of a thick medication).
Side-Port Type Needles: The benefit of the side delivery system is that the medication is delivered over twice the area of the regular needle. This makes for a smaller injection site and the medication is absorbed much quicker into the system of the animal. Even if the syringe misses its target the syringe can still empty even if it has hit the ground as the point will not be filled will dirt or trash.
In urban settings where there is an opportunity for someone finding a lost syringe Side-Port type needles are a good choice. (Animal Controls many times choose this needle for this reason)
Plain needles: Many times plain needles do not stay in until the syringe is emptied. Some people know this and increase their drug dosage to cover the loss of medication. With the smaller syringes (1and 2cc) the animal will probably get all the medication. If using a plain needle the Sideport plain is a good choice.