This is to help people better understand the new perks and weapons and their uses in my opinion. I hope this helps some people.
Bowie knife/Sickle have the same stats. They are a 1 hit kill through round 9 versus walker zombies, 11 versus dogs/monkeys/smokeys. In BO, you lose the knife if you die (not downed, dead). This is a change since Der Riese. Why they did this and kept the price so high and nerfed it, I can't say.
Gersch device: This is a close relative of the monkeybomb. It draws zombies away and kills the ones that get pulled into it.
Matryoshka Dolls: These are another new grenade that throw out 3 different colored grenades in the direction that you are facing. These are much stronger than regular grenades or Semtex.
PHD Flopper: This is a strong new addition. This perk does 2 things; 1. You can 'dolphin dive' off of a height to get a strong explosive effect. This works on fairly high level zombies, and 2. this protects you from self-inflicted damage. Use the Ray Gun, Scavenger, grenades, all without fear of killing yourself.
Stamin-Up: this perk is like Marathon/Lightweight. It isn't necessary, but a great help in kiting zombies around the map.
Deadshot Daiquiri: This perk gives a Steady Aim effect and brings the reticule onto the zombies face when you ADS (aim down sight). Some love it, most think it is a complete waste. If you have real trouble with headshots, get it, but I don't recommend it.
Thunder Gun/ Zues Canon: This is a wind gun that sends out a wave of air that destroys zombies in a nearby area. If any zombies seem unaffected, shooting them again immediately will do nothing, so just get away quick. The correct way to use this is to run a circuit around the map or an area and only use it if a zombie blocks your path. Use your regular guns when you get to good spots to fire on the zombies, then pull this out and continue the circuit. Gathering groups of zombies to blow them all away is a waste of ammo and points. Use sparingly.
Winter's Howl/ Winter's Fury: This is a freeze ray gun. The proper way to use this is this: Run a circuit around the bottom part of the middle level (Warroom) usually solo or 2 people. Fire the freeze ray at the crowd to get them to slow down which will cause them to migrate towards the middle of the level (where the TP is) so that you can continue to run around the outside of that room. Keep shooting the fast zombies that spawn, while leaving the majority to wander around slowly until they stop loading. Then make crawlers if needed and kill the remaining slow zombies. Again, using this to wipe out crowds is a waste of ammo and points.
V-R11: This is a gun that makes zombies into humans. The idea is similar to the previous guns, run you circuit, fire only at zombies that block your path. The zombie becomes human and some regular zombies will follow him.
Scavenger: This is a sniper with explosive rounds. Large radius explosion, I recommend using this with PHD Flopper to protect yourself.
Ascension Monkeys. Once you have a perk any round could be a monkey round, they generally come about every 4-5 rounds after that, but it varies. They come for your perks as well as to attack you directly. If you fend them off without them every touching a perk machine, you get max ammo and a free perk cola. If they touch any machines, you get no free perk, but still get max ammo.
Gearge Romero: He follows you around like a round 1 zombie unless you wound him, then he runs after you. He stuns you as well as inflicting damage. You must run him into water or kill him to get him to stop. When zombies pass near him or he gets enraged (like you shot him), he will swing his overhead light (looks like a hammer) and this makes all nearby zombies into super-runners. His light also shows his health; from blue (healthy) to reddish and sparking (near death). He tends to glitch out of the map or just stands in a corner somewhere. He drops a random perk and Death Machine/Wunderwaffe when he dies (depending on whether or not you did the easter egg).
[more cheats for Call of Duty: Black Ops here]