Rule of these films: if you’re a truck, that makes you a tough-ass warrior (most of the time at least). But there is enough variety in these films (sportscars, military vehicles, construction vehicles, racecars, and a Hummer) towards the Transformers.

My vote goes to Megatron’s tank truck. It’s G1 Motormaster, RID Scourge and every Nemesis Prime all wrapped up in one mean road machine, the perfect challenger to Optimus’ Peterbilt. It’s an utter shame that vehicle was not seen more often, especially in an action scene.

Runner-up goes to Ironhide's pick-up truck, for being tough as well as fast, which fits Ironhide well.

 

I really liked Sentinel's Airport Firetruck. It's "exotic" enough to differentiate him from Optimus, even though they're similar in terms of implication and size/shape, and it's a really interesting vehicle, from a technology perspective. Fits the character of a scholar-warrior-Autobot leader pretty well, I think.

 

I loved Megatron's tanker truck. It's this massive intimidating vehicle, outlined with spikes and jagged edges, as sharp and feral as the robotic form, and yet it's rusty, covered with a tattered tarp, dull and brown, dusty; it's a deprecated and ravaged vehicle, both violent and injured, just as Megatron is, alone and wounded in the desert.

It's wonderfully fitting for his position in the third film.

 

The tanker truck. I never thought of Megatron as being a truck, but this is one of the things that actually worked really well in the films. That truck just screams "evil."

 

Megatron's tanker truck. That thing was awesome.

 

Longhaul's dump truck mode was massive and useful.

Megatron's Mad Max Mac looked awesome but it wasn't the right alt mode for him.

 

So you forgot Ratchet? I like Ironhide's, its tough and extremely badass looking.

 

M i x m a s t e r

 

Sentinels vehicle mode was amazing, huge, and mighty. Ironhide I love, that and the fact of you can buy a replica for under $100K.

 

Megatron. He finally has a honest to god earth mode.

 

Does a cement mixer count as a truck? If so that would probably get my vote. But regarding the options here, I would probably say Megatron.

 

Megatron's truck mode. Too bad it had a total screen time of about 3 seconds

 

Let me just put some pics here, time to open up the Movie folders on my pc anyways.

Still amazes me how big Ironhide is in truck mode.

 

I loved Megatron's alt mode in DOTM. But I got to with Ironhide's vehicle mode. It was pretty badass and had more screentime than Megatron's  

 

That Topkick is one fine looking vehicle  ! Definately has my vote.

 

I've been trying to decide which, but I'm going to call it a tie between Sentinel and Megatron. Sentinel's looks heroic and regal while Megatron's looks twisted and gritty and both transfer these features to robot mode very well giving the two antagonists a great contrast.

 

Ironhide's truck.

 

Tanker truck. kinda disappointing there is no leader class on that.

 

Sentinel's altmode was magnificent. I love that truck anyway, and watching it turn into a giant robot (or vice versa) pretty much made my day.
That said, Mack Daddy Megatron still wins for that Mad Max-ed out brute of a tanker truck. Everything about it was perfect, and if you've ever seen it in person, or pictures of its detail work...just wow. It's huge and menacing and rough and everything an 'evil tanker' should be. Macks make some mean looking trucks anyway and they really took it to the -nth degree for Megatron...as it should be. My only lament is that we see it on screen for a grand total of like...fifteen seconds? over the course of the whole movie. What. A. Waste.

 

No, I already mentioned him in my OP. He's a Hummer, not a basic truck.

Perhaps... but it's still very much a construction vehicle. I was going for basic truck modes in my poll.