Best muscle relaxers for muscle pain?

Ask your PCP . Various drugs have been developed to affect the muscle contraction. Commonly used centrally acting muscle relaxants includes Lioresal, Soma, Flexeril, Skelaxin, (metaxalone) and Robaxin. Infrequently used muscle relaxants include Norflex) and Zanaflex. Many side effects include drowsiness, dizziness, headache and lethargy. Ask your PCP to adjust the medication for your needs.
Many. Cyclobenzaprine. Methocarbamol. Tizanidine. Benzodiazepines as a class. Not all work the same for everyone so there is no "best." Non steroidal anti- inflammatory drugs work well for relieving pain although they do not "relax" muscles directly.
Acute or chronic? You should check with your doctor but in reality I'm not terribly impressed with the most commonly prescribed muscle relaxant agents. I would avoid medicating if possible unless you are truly suffering from an injury of some sort. Ice or heat depending on acute or chronic pain. There is a great device called a Sootheaway machine (www.sootheaway.com) which we distribute at the VA and pts love it.
Tizanidine. All doctors tend to have their 'favorite' one. I prefer tizanidine (zanaflex) because it is not as sedating and seems to help more than cyclobenzaprine (flexeril).