What kind of pills was Tommy Riordan taking?

From an interview with Gavin O'Connor, the writer and director of the film:

The Tommy character reminded me in some ways of Mark Kerr, who was the subject of one of your documentaries, The Smashing Machine. How much did your experience from that production inform the sensibility of Warrior?

Smashing Machine was my introduction to the sport and the fighters in the sport. But since that film, I've met so many fighters and have been to so many fights and watched so many fights that that was just part of the DNA of what I was doing. I'm sure there's a page out of a lot of even boxers' lives, and people I know, that have sort of infiltrated the script.

If you're referring to the pills ... now that you mention it, probably unconsciously. The whole intent with Tommy was, he was coming home to see his father -- but he was coming home to see the father that he knew when he left, which was a man who was a drunk.

In the documentary (linked above), the fighter, Mark Kerr, is linked to prescription painkillers (opiates). While the reference does not tell us plainly that Tommy is using painkillers, it's a reasonably good pointer in that direction. All the familial issues that Tommy has had as well as his experience in the marines might explain why/how he became addicted to them. It's useful to note that opiates, besides dulling pain, also promote a sense of well-being and euphoria.

Prescription painkiller abuse is quite rampant nowadays in all strata of society.

Since there is no hard-evidence in the movie that would suggest either, nothing can be said definitively. But, I would say that those pills would most likely be anti-psychotic (neuroleptic) or anti-depressant of some kind.

The reason I say this is because Tommy (Hardy) is shown to have a tough childhood (mother's chronic illness and death, father's drinking issues) and later on his buddy in the Marines dies in friendly-fire, that eventually leads in Tommy going AWOL from active duty. Now I reckon, such scenarios are enough for any sane person to develop psychological issues.

NOTE: A friend suggested that he might be taking steroids, but that seemed a little off to me since Tommy was in the Marines (where I suppose steroids that are not prescribed would not be allowed) and frankly I doubt Tom Hardy's physique (though mammoth) is a result of steroid popping!

Most likely (from military perspective)

Seroquel (antipsychotic) Trazodone (sleeping/antidepressant) Zoloft (antianxiety)

Military doctors work on sliding scale. If one medication doesn't work, up the dosage. if higher dosage doesn't work, change medication, ad nauseam. These are most often prescribed for said conditions

Painkillers. Probably opiate based. They numb mental / emotional pain. They also alleviate the symptoms of post-traumatic stress.

When Tommy's Dad refers to Tommy sounding like a 'maraca' walking in here means he rattled as he walked because his pockets were full of pills.

The pills are painkillers. On the side of the pill bottle, it says Darvocet.