They waste your money, can cause undesired effects, and if used when not needed will eventually be useless when needed. Aspirin, Acetaminophen, Ibuprofen, Naproxen, etc. can be used to treat aches and pains. Fever seems to weaken the virus, and shorten its life. The body is wise. It's probably best to leave a fever alone unless it makes you uncomfortable.
Decongestants lessen congestion which prevents drainage, making bacterial infection more likely.
Pseudoephedrine, phenylpro-panolamine, and phenylephrine are equivalent so buy price. Each are mild stimulants and might interfere with sleeping. Given the choice, I choose sleep over having an open nose. Nasal sprays work well without the stimulation, but if used more than 4-5 days they will cause swelling, not relieve it. Yes, if you're coughing and the cough isn't relieved by saline nasal irrigation.