as the title says are these worth taking?

Grimgor (i already plan on using blorcs)
wyvern
doom diver
giant
Ogre mercs

so basically i'm debating on what i want to buy next and need some input, as for grimgor, i'm gonna make a conversion for him so i really just need to know whether he's worth using or not

Hiya,

These fine points have been discussed much in these forums. If you did a search, you could probably get a number of threads that go into greater detail. Still, I can try to distill the general consensus on these things. Remember, though, that having everyone not like something doesn't make it a bad idea. It's always best to find out for yourself. If you can proxy with some friends, that's the best way to find out.

Grimgor: There are many people on the forums that dislike special characters. They don't like to play any games with them. Still, Grimgor is a combat beast. He will most likely slaughter anything he can get his clutches on. The biggest problem comes in what he can get his clutches on. He works great for a game or two against an opponent, until your opponent figures out that he is best left alone. Grimgor can be re-directed pretty easily with cheap units so that your opponent never has to fight him. He's only M4, which is pretty easy to avoid. Other than that, he will kill whatever he can get to.

wyvern: Many people say that with 7th Ed, these things are a must take. I love 'em. Everyone hated them in 6th Ed and I had a nicely painted model of one. I always wanted to use him. In 7th Ed, it's rare to see a tournament army that doesn't use them. The best way to think of the wyvern is to think of it as a flying, terror-causing vehicle to get your general into combat. It can't outfight dragons or other powerful beasts. It is meant to cause terror (and allow your general to be immune to terror) and get your general to where he needs to be. You should learn to get good with him, though. They can be shot and magicked easily and need to almost always be in combat to get their worth for the points. Still, it's not that hard to learn and is a lot of fun. I love the wyvern. There are rumors and pictures of a new wyvern model floating around, but no one knows what is the real story with it or if it's really ever going to be released.

doom diver: Some people will tell you that this is the best war machine that OnG can take. They love it and do amazingly well with them. The ability to hit and always do d6 hits with no armor save makes it great for knights, skirmishers, or other high armored targets. Personally, I have a hard time hitting with them. The scatter dice aren't my friend and I seem to only get a direct hit 1/20th of the time (instead of 1/3). People will say, Oh, well, when you get good at guessing distances, you will be better. I say I am pretty good with distances, but I alway seem to scatter 8-10 inches away! d3 re-direct helps some, but I never seem to hit with it. Still, they are a lot of fun and if your luck isn't as bad as mine, you should really cause some damage with them. They are one way for us to really take out knights.

giant: Giants are hit or miss...and by that, I usually mean that they are either killed by missile weapons or they smash their enemy. A lot of people love giants and I have to admit that after a few years of avoiding them, I like to use a giant in my army list. If you go against a gunline, you will have a hard time keeping him alive. Some people will say, though, that if he lasts a couple turns and then dies to shooting, that he was a good distraction for the rest of your army and helped them get across the field with less casualties. One of the biggest weaknesses of OnG is dealing with large monsters. The giant is great against them. Look at his attack chart vs large opponents. I've had mine splinter a treeman in one hit before. They are great for crushing hydras. Just watch out for high strength opponents that can dish out the attacks. I've had a good rolling unit of dryads take down my giant pretty fast. Overall, I say the only reason to not take a giant is an enemy gunline.

Ogre mercs: I've asked about this and been told that the only good ogre mercs to take are ironbreakers (that is the oger unit and not the dwarf one, right?) and maneaters. Regular ogres do not have enough armor and aren't any tougher than orcs. They are faster and they cause fear, but will get shot or magicked before they get too far. Other people have had good luck with ironbreakers and maneaters. Most people haven't tried them, though.

Hey, have you looked at the Battle fo the Bosses web campaign? It's a great way to have your average warhammer games turned into a greater campaign with good fluff and stories. Check it out!