Varsol. Use to be common in parts washers. Works well on many adhesives, and great on chewing gum, but you might have to follow it up with soap and water to remove the oily residue.
Mineral spirits is similar to varsol (slightly different composition due to distillation fraction).
Acetone works, is less toxic, but evaporates fast.
Methyl Ethyl Ketone is stronger than acetone, and has a higher toxicity. It also evaporates quickly.
Depending on the adhesive 95% alcohol can work.
All are organic solvents/diluents and can screw up plastic and finishes (depends on the composition of the plastic/paint). All are flammable, so ventilation and safety are advised. Acetone and alcohol can be diluted with water, but it will reduce efficacy. All can be bought at Home Depot, Lowes, or your local hardware store. Be safe.