The information below is intended as a guide to the typical tactics used to sabotage vehicles. For crime prevention and reference use only.
Tires are typically slashed/punctured. An ice pick, sharp knife, or anything that wont break or bend will work. Putting a hole in the side wall will make it impossible to repair.
If someone REALLY wanted to fuck up a car they could use a product called JB Weld. It's just about as strong as an actual weld but silent and discreet. It can be used to immobilize most any vehicle component. Any person who's used JB Weld can attest to it's strength.
For example JB Weld can be used to weld lug nuts to the rim. Simply fill all around he lug nut, completely filling the lug nut well. After the JB Weld cures puncture the tires/cut the valve stems or just wait for the person to get a flat. The vehicle will inevitably need to be towed to the shop. If they're lucky, the mechanic will get the wheel off somehow. Chances are they'll need a whole new axle. If all 4 tires are disabled in this manner just getting the vehicle moved onto a flatbed towtruck would be a lengthy project.
You could also JB Weld the doors/hood/trunk of the car shut. JB Welded oil drain plugs, locks, oil filters, gas caps and other components are sure to lead to interesting problems.
JB Weld has different products in different forms. The form you need would depend on which of these ideas you use. Industro Weld (large size tubes of JB Weld) should be fine for most applications. JB Stick is a putty form that is easier to work with in certain applications. JB Kwik cures in just 4 minutes but is a bit weaker, ideal for locks. Waterweld is also useful as the surface does not need to be clean and it will cure even under water or gasoline.
Radiators are an easy target. They can often simply be stabbed with a screwdriver through the front grille. A box of quick rice in the radiator will expand as the vehicle runs and clog the works. About a pound of salt or some Drano will eat away at the radiator's copper tubing.
The stereotypical sabotage technique is sugar in the gas tank. This will merely block the filter, and do little damage. More effective fuel tank additives are sand or 10 to 15 mothballs.
The best sabotage target is the lubricating system. If incapacitated, it will cause the engine to overheat, bind, and generally destroy itself. Karo syrup in the oil filler hole is another classic that, in reality, only effects the filter. One option for major damage is to carefully remove the oil, either by punching a hole in the oil pan, or removing the drain plug. Adding water to the oil is more effective, since it will not lubricate, but will keep the oil pressure up, keeping a warning light from coming on. Better than water is diesel or gasoline, as it will also break down existing oil.
For maximum effect, look to adding abrasives to the lubricating system. The oil filler hole is not the only option here. All moving parts need lubrication, such as transmissions, differentials, and wheel hubs. Many lubrication points will have screw on caps that can be removed with an adjustable wrench. Sand can be used for this as well. However, the top of the line abrasive is the kind used to polish stones in tumblers, available in hobby supply shops. A very fine powder grit mixed with a slightly more coarse fine sand grit will have the best chance of getting throughout the whole engine and wrecking everything. A 400 and 600 grit size mix works well. A mere half pint of this will completely destroy an engine.
Pouring sand or grit can be difficult, especially at night, so here are a few ways to make it easier. Attach a couple feet of flexible plastic tubing to a funnel for increased and easier reach. Or get a grease gun, available at auto parts stores, remove half the grease, mix in grit, and apply with the gun. Another option is to put the grit in a condom, tie it off, and simply drop it in the oil filler hole. After running for 30-50 minutes the condom will dissolve and release the grit.