Enclave deathclaw
Deathclaws are some of, if not the most, dangerous creatures in the wasteland. A Deathclaw will not back off of any prey it sees so unless you think you can kill it, run. There's no shame in running and hiding until they go away or until you can get the jump on them. Deathclaw attacks can usually end up in a one hit kill for players level 1-10 so keep your guns loaded and start blasting their legs first.

If their legs are crippled they can no longer perform their pounce attack. Being their main attack this will lower the danger level considerably and also make them quite slow. In Fallout 3 having the Dart Gun works perfectly for this type of thing. After crippling their legs start unloading some shots straight to their head. These creatures are upgraded even further in Fallout: New Vegas, gaining a 25 Damage Threshold and also being much more numerous.

Deathclaws no longer spawn randomly as they did in Fallout 3 but when you step into a breeding ground for them, you are basically done for.

Death Breeding Grounds are located in Quarry Junction, Deathclaw Promontory, North I-15 and Deadwind Caverns. These creatures do not like to play so if you even see one and it hasn't seen you yet, turn around and run! In Fallout: New Vegas, basically the only way to kill them is to combine: an anti-materiel rifle, armor-piercing rounds and a Stealth Boy. If you're an Energy Weapons person, Gauss Rifle with Over-charge microfusion cells.