My thoughts on these units:
PAB-28: Like the fluff says, not a line combat unit. This thing would be terrifying in an RPG. That said, if you absolutely must take this onto a TW-scale battlefield, it might make a decent ambush unit, going for the swarm on a command 'mech.
Sea Fox: Another suit not meant for line combat, though as the fluff says, it can excel in defensive operations, since you'll only deploy it where it would be useful. The 1-hex jump is interesting, though I'm not yet sure where it'd be most useful. Leaping out of shallow water, perhaps? Would definitely be nice in a RPG, where it can jump decently without the noise and light of jets. Do note that the presence of the cutting torch and LMG together makes this a VERY good boarding suit. Use them to defend the undersea command posts the Davions are fond of, or to try and take some of those large naval vessels Kurita has fielded. (I now want to play an RP where a Sea Fox team must board and neutralize a Subcapital Triton before it can move into position to blast attacking forces in a Davion counterattack.)
Fusilier: As the fluff says, this isn't a shiny suit(reflec armor notwithstanding). It reminds me of the Ravager, another one that focues on armor at the expense of mobility or firepower. With that in mind, I would definitely use this as a defensive suit, anchoring a strong point or defending Haurberk squads while Grenadiers, Cavaliers, and Pumas do the offensive jobs. Might also be a good unit to attach to the Destrier, in order to protect it while it does its work.
Kruger: It's an armored car, no more and no less. Reading up on tactics used in North Africa in WWII teaches you how to use this. Heck, it kinda looks like an Sd Kfz 232, and should be used in a similar role. It's a strategic scout instead of a tactical one. It doesn't find hidden ambushes with probes, it patrols the countryside until it finds enemy formations, and then sneaks off to report their position. If it finds a light target of opportunity, it can attack. Could also make a decent support unit for infantry, having the range and speed to add a bit of 'oomph' to a conventional company or a battlesuited platoon. Much like the Capellan TRO, this unit has inspired me to step outside my usual faction for a bit and try and built a light guerilla force. I think anyone involved would approve of such a group of 'Desert Foxes'. ;)
Marten: Like the Kruger, this is a strategis recon asset instead of a tactical one, though the remote sensors can be quite useful on a tactical basttlefield, especially when placed by something this fast. I want to attack a lance of these to a force of Ant Lions, and drive people absolutely mad. >:D
JI2A1: I'm gonna call this a 'Jitoo' for the sake of my tongue. Fast, decent cargo bay without getting excessive, missile-based support armament...what's not to like? I'm sold. 8)
Hasek: Okay, I'm usually one of those who prefer fluffy or challenging units over the optimized stuff, but this thing is just TOO good. It covers every weakness of infantry while still having transport ability? [drool]
Sortek: DAMN, that thing looks goofy. ;D Looks like a good unit for harassing conventional forces, either rapidly wearing down battlesuit squads or parking tanks. I suspect that Sortek crews have a one-word vocabulary when in combat, either on the attack or during withdrawal:
AAAAAAAAAHHHH!!!! :D
Zibler: Yup, it's an IS Epona. Yup, it's awesome. Yup, my RAF gets it. Aw, yeah... 8)
Hanse: Despite the lack of turret, I kinda like this thing. It's a superheavy tank destroyer, not an MBT. Use it as such, and you'll do fine, especially against other conventional units.
Sniper: Combination Artillery and Mobile HQ, with amphibious ability. Sold. My favorite part is actually the comm gear, which gives your force an initiative bonus
and lets you monitor large numbers of remote sensors(see the Marten) to spot for your own shots. Win!
Paladin: By the Pantsless Ones...TWO full-sized Long Toms on a turret?! Only now do I truly understand the term 'awe-inspiring'. [drool]
Destrier: Those magnificent bastards, they finally did it. They built the Land Battleship
Excessive!
AHAHAHAHAHAAA!!! [wildandcrazy]
Prey Seeker: Yet another strategic scout(Davion are big on seeing the big picture, it seems. I see nothing to complain about.), when not doing far recon, this thing has one target, as quoted directly from the TRO: Soft rear areas. As with all other scout/recon units, keep this thing focused on that goal, and you'll do fine.
Gunsmith: Another crazy fast raider. If any of you Davion fans have gotten this far, seen all these scouts and raiders, and aren't thinking evil thoughts about what you can do to make life hell for Kurita or Liao occupiers....you're doing it wrong. }:)
Hollander III: Okay, this one isn't a guerilla fighter. It's a line combat unit, provided you remember that it is a
light line combat unit. Use it to stiffen light formations, or act as an escort for heavier fire support units. Might also make a good infantry support 'mech, where that cannon can help make short work of buildings or enemy battlesuits, to say nothing of enemy IFVs.
Scarecrow: Mmmm....war crimes on legs... {>{> Yet another raider(pay attention, Davvie fans!), this thing is very clear in its role as the terror in the night. This. Is.
BatMech.
Antlion: Finally, a decent Mortar 'Mech! O0 This is very clearly a support and harassment unit, meant to fire indirectly either with data from its own remote sensors(or from someone else), or from a physical spotter. Remember that Mortars do have an S-G ammo type; keep a TAGger handy. Also, is anyone other htan me absolutely convinced that these things are derived from the Blue Flame's chassis?
Centurion: A trooper Omni that's a solid combatant in every configuration. I think we can definitely call this one a win for the Feddies. My only complaint is that most of the stock confurations are too genral-combat, and we're not seeing any of the specialized configs that can truly make use of the Omni ability.
Vulpes: Despite the fluff, I would not use this to fight at range. Instead I'd use the armor to safely close, using a single laser to keep enemies honest. Once you get to a decent medium range, drop the stealth and unleash heavy volleys from your warload. If/when you get hot, hold your fire for a turn or two, using the stealth armor again to keep you safe while you cool down. At no point should you get into pointblank range.
Black Knight: Damn, this thing's a monster. FedSun fans wanted a stalwart defender of the realm, allowing none to pass? You got it right here. O0
Templar III: Another rock-solid line combat design. I wanna see a B catch a Shiro with that whip and see just how long that hardened armor will last under an assault-weight hatchet. }:)
Atlas III: Like it's been said before, this thing is a command 'mech, not an assault 'mech. It doesn't dish out damage, it keeps the pilot alive. And DAMN, does it do a good job of that.
Rondel: While I imagine many FedSun players were outright pissed when they lost the Dagger production line, I think they've more than made up for it with this. Fast, powerful, and ridiculously tough(Seriously, a Clan PPC won't threshold that nose!), I think House Davionhas air superiority covered.
Cutlass: Like others have said, it's a leaner, meaner Stuka. I espeically like the elctronics, making this an absolute terror in space combat.