Unfortunately with the Ogre book being written during 6th Edition so they have, drum solo please, DUN-DUN-DUUUNNN!!!, a restriction.
5) 1+ Bulls unit
Now the Bulls aren't bad as a unit, on paper. They look quite tasty. and it is only after you have played a few games that you realise how different 'on paper' and 'reality' actually are. You are going to need to get the charge first off. Ogre Bulls can't function as counter-punchers. Even when you tool them up with armour and ironfists they are still pretty poor.
Most Ogre players use Bulls in small units of 3 and use them as throw away units (or MSU [Multiple Small Units]) or speedbumps. Some Ogre generals use Bulls as a Death Star. This tactic will me mentioned later in the Ironguts section as they are normally the unit that get Death Star-ed.
Gnoblars suffer from a watered down animosity that is similar to Orcs and Goblins, but they get no good result. They have 'OOOHHH!!! SHINY!!!' where they spend a turn fighting over something or you can move them normally. They are worse than Goblins too.
Gnoblars were very hard to like from a modelling perspective. You only get so many bodies and you mess about with the different heads. Not only that they are only 2pts each and I didn't want to paint that many models that are worth bugger all.
They also have a restriction...
7) You can't have more units of Gnoblar Fighters than you have Ogre Bulls.
This restriction doesn't really kick in until you start dealing with the Special choices, but it is another thing that restricts your choices.
Trappers on the other hand are worth every point spent on them. Being able to scout and march block from the off can annoy the hell out of most generals. I've had my Trappers fired at by a multitude of things which completely outweigh even their potential effectiveness. They do have an option for a champion that is BS4, but I only get him if I'm shy of points. The only issue is that they have a horrible restriction.
8) You can have a single unit of Trappers in your army. You may add an extra unit for every Hunter in your force.
OK, so I have to give up on my magical defence/offence to get one of the best units in the Ogre list?
I normally use them in units of 8 or 9. 9 is better than 8, due to casualty tests, but other than that I never expect them to see the end of turn 3.
I know that some of these guys are unpainted and I apologise for that (I also have another 5 squirrelled away). I'm trying to be enthused to paint Gnoblars, but I can't...
Well that took a hell of a long time. I'm going to post this and go and do other stuff.