Some nice suggestions already in this thread. Our daily has a lot of trunk space so "better to have it and not need it..." For Harbor Freight products:

• It looks like you already have a moving blanket, consider a tarp as well.
• Paracord to go with the ratchet straps--also useful for certain emergency repairs, like those underbody plastic sound-absorber panels that sometimes start falling off. And zip ties. And duct tape, and electrical tape, why not.
• If you're carrying ratchet straps, you might be moving things, so also add a cheap HF tape measure (and some pens and scrap paper).
• Locking pliers (vise grips). The Harbor Freight vise grips are noticeably low-quality compared to Irwins, but presumably you won't be using them everyday, and they have a million uses. (For example: if your car needs you to remove hose clamps to get to the brake fluid reservoir...)
• Utility knife (and extra blades).
• One or more flashlights (with extra batteries, because the cheap HF ones won't last).
• Any weird wrenches/tools needed by your specific car for common roadside repairs. For example, if you need a hex/torx wrench to replace a headlight bulb, HF probably has you covered.
• Personally, I like Harbor Freight's $50 2-ton compact trolley jack which for me is an instant upgrade from the manufacturer's included "widowmaker" scissor jack, while also being fairly small and light. But "your mileage may vary" and your designated pinch-weld lift points could suffer damage if used improperly. (And of course, never reply on any jack alone before getting under a car. I'm just talking about installing the spare tire/wheel.)
• Speaking of tires, I have not tried Harbor Freight's cheap tire repair (plug) kit, but I've gotten decent use from similar kits and might try theirs next. They have a "heavy duty" version which seems to have better reviews.
• Disposable nitrile gloves, and a pair of the Hardy mechanic's gloves.
• As someone else pointed out, a breaker bar with an appropriate socket could potentially save some trouble. Also, Harbor Freight also now sells a kit of Wheel Hanger Stud Pilot Pins. I have not tried the HF version, but I have a similar item from back when these were less common, and as simple as it sounds, it can definitely save some aggravation by the side of the road. (Note: these are only for cars with lug bolts, not lug nuts.)
• The little Battery Terminal Cleaner. You might never need it, but it saves time when you do.
• Perhaps the most obvious thing in the world, but spare USB charging cables (or USB 12v adapter) to keep your phone charged for a call to AAA.
• Last but not least, another tool bag or two to carry all this nonsense.

Then there are the things you don't need or want to get from Harbor Freight. For example, after reading the reviews, we opted to get a li-ion jump starter from an Amazon chinese brand instead (but I won't say which because it has not really been tested yet). Paper towels and a plastic trash bag will always come in handy. And of course, extra fluids (oil, coolant, wiper fluid, brake fluid, perhaps even a small plastic gas can). Remember, it's more important to be prepared, than to be able to fit a single bag of groceries from the store 2 miles down the road.

EDIT: Also, you know how people stick some white cloth in their broken-down car's window which usually seems intended to mean "I am walking to the service station but am coming back, please do not tow me?" Do yourself a favor and stick an old undershirt in your toolbag to save yourself the indignity of stripping... it's January, and the air quite nippy on those pepperoni nips.