The genes that make geckos feet sticky into a tiger. Because that would be crazy cool.

Well, the gecko feet stick because they have so many protrusions that it creates a huge surface area of contact. This large surface area involves a lot of weak van der Waals forces that add up to be stronger than the force of gravity on the small mass of the gecko. On a creature as large as a tiger, this effect would not be possible with normal physiology.

Well then that idea is shot.

give chickens eagle's wings

Do you mean mixing diffrent animals together?

Sort of. For example, bacteria multiply incredibly quickly, so scientists can insert genes from other organisms to produce proteins in fairly large quantities quickly. Insulin can be manufactured cheaply in this fashion. I know in reality that most traits are polygenic and many genes are pleitropic, but I was looking for things like "lizard limb regrowth on tarantulas" or "bombardier beetle glands in skunks"

Clearly you were disappointed.

Put the reproduction speed of a rabbit into endangered animal species. Problem solved