The Titan Cannoneer is based off a simple concept- it's a big titan holding a cannon! It's also such a pain to put together, it had better be worth taking, right?
Slow speed, which isn't a huge issue given his role. Low MAT and RAT, good DEF and ARM, average FURY/THR. A bit more expensive than his Gladiator brother, at 9, he also has few health boxes, especially for a heavy.
His first and most distinctive weapon is the Siege Gun, a mid-range, decent POW weapon with AOE 3. With his low RAT, you're not going to be hitting much, even with aiming. With boosting, you'll hit most things, but regardless the AOE is nice. He also has Tusks, which increase the strength of his head-butt and slam power attack damage rolls, as well as a War Mace which hits pretty hard.
Obviously, the focus of this beast is the siege gun, which is strong but not likely to hit without fury spending (which you probably will, so not a big problem). I wonder at whether or not the Titan is really going to be more useful overall than the Venator Catapult Crew, who has another half a foot on their range. I suppose I'll find out with more plays, and actually trying the other unit.
His Animus is Diminish, which lowers the strength of enemy models within two inches of the user. It's an interesting tool, even though it can only be used on the Cannoneer or the warlock. In melee, in turns the Cannoneer into a more survivable beast than the other heavies Skorne have available (aside from the Sentry), and it can help keep the warlock alive when the opponent gets up close. It also can make it easier to throw targets, especially if combined with another STR enhancement on another beast. Overall, it's a very handy animus which should give the Cannoneer a place in lists.
Bullheaded: Same as with the Gladiator, this changes the way the Cannoneer frenzies. He'll slam instead of charging. Overall, this can be very useful at the right times. Once your opponent has moved his army up into your army's face, leaving fury on the Cannoneer isn't nearly such a big deal- if he frenzies, he could make the battle a lot easier for the melee elements of your army.
Master Tormentor Morghoul: Not too much, here. Diminish helps Morghoul's survivability, but not enough to save him if he gets seriously threatened. Admonition can help keep the Cannoneer out of combat.
Titan Gladiator: Not really anything exciting here- Diminish helps the Gladiator throw things more easily. They are designed for very different roles, so not much synergistic overlap.
Cyclops Savage: If you're running enough beasts, the Savage is very handy- Prescience on the Cannoneer can really keep your Gladiator's fury usage to a minimum. If you're aiming at that DEF 15 warlock (needing a 9), you can roll and see if you're close before spending the fury to boost the hit, saving the fury for the damage rolls. These two go very well together. Also, if they are close, Diminish can be awesome for keeping the Savage alive, since he's quite fragile otherwise.
Paingiver Beast Handlers: Medicate is the most useful ability here, since the Cannoneer doesn't have that much health. Enrage may be nice to make the Cannoneer useful on a critical turn as well.
Usable in all the same theme lists that the Gladiator was. I could see him having a place in Dominar Rasheth's list, just at a guess, but since I've not used the warlock, I can't tell quite yet (since the Sentry may be a better choice).
Overall, the Cannoneer is a fairly well-rounded beast, with both ranged, melee, and support elements. He's capable of providing some use the entire game, unlike some of the other Skorne options who are melee geared. I think he's a little overcosted myself, since I don't find him any more useful than the Gladiator (who's a point cheaper), but I imagine that opinion will change upon facing more infantry-centric armies. Regardless, you can't go too wrong by taken this guy.