This is by no means an exhaustive guide, but gives you a rough idea of where to go for a drink in the capital of the Savo region. I haven't been to nearly every bar in town, but as I do research I will update.
KeskusBaari
(*****)
This bar is an institution. It's been around since forever, and it's still owned and run by the same guy, who sometimes tends bar. He's the smallish guy with curly gray hair and glasses. His name is Make. Say hi.
KeskusBaari is a small and cosy pub. On weekends, cramped might also be a good word, considering its popularity. In the summers, there are also tables outside on the sidewalk, which helps to some extent. The music is quiet and tends towards classic guitar rock of a downtempo variety - Pink Floyd is a staple. Prices are reasonable, and they have Guinness on tap. It's good. Go there.
There are no bouncers. There is no coat check fee. There is no dress code. Age limit is 20 on weekends.
Stoppari
(***)
This medium-sized dance bar caters mainly to the 18-25 crowd - as proved by their failed experiment in trimming off the rowdier element of their clientele by raising the age limit to 20 on Saturdays - the bar was empty on Saturdays, both the sub-20s and their friends having gone elsewhere.
It's back to its former glory now, though: Pretty full on Fridays and Saturdays, it is extremely crowded on Thursdays, when a kind of Happy Hour starts at 6pm and goes on until closing time. For this time the usually somewhat high drink prices are supplemented with cheap offers on a variety of things, including beer. Be prepared to stand in line if arriving late at these times.
Music tends towards the usual chart hit stuff, with Britney Spears and boy bands regrettably common; 70s disco and funk hits occasionally surface though, and most of the DJs will gladly play "Sex Machine" if only someone requests it. At least one DJ sneaks in as much reggae as he can, and sometimes jags of trance can be heard towards the end of the night. The sound system is fairly good and the dance floor is of a reasonable size for a bar this size. Oh, and it's loud in here.
Decor is currently very mildly Tex-Mexish in places for no apparent reason; tacos and chili burgers can be had from a corner of the non-smoking section. Said burgers are exceptionally good, and well worth the asking price, although some of the bar staff do manage to mildly fluff making them.
Stoppari is just around the corner from the marketplace, near Suomi Grilli. Roller is a good place to go next, staying open until an hour after Stoppari closes - just head across the marketplace from corner to corner. When leaving late at night, resist the temptation to get a burger from Suomi Grilli. The fries are pretty good, though.
There's no getting in in scruffy clothing - this includes track pants. There is a nominal coat check fee in the evenings.
Roller
(***)
Rock'n'roll. The music here is all air guitar all the time, in various flavors from Rage Against The Machine to Creedence Clearwater Revival, there's a pinball machine and a pool table, and an inexplicable racing car takes up way too much space in the unfortunately cramped premises.
The prices here are marginally lower than Stoppari, but don't drink any special house concoctions, especially if they're still trying to offload the sheer horror in a shotglass that is Jorma.
Coat check is voluntary, and as far as I know they don't give a toss if you show up in a swimming suit and goggles, if that's how you like to dress for barhopping. The bar is located at the opposite corner of the marketplace from Stoppari and Suomi Grilli.
Downstairs from Roller is Zic Zac (*), a cheap, nasty version of Stoppari. Bigger dance floor, stupider, younger, and more intoxicated teenagers, poorer lights, worse music, and marginally lower prices. Don't go if you can help it.
Also, there's a pizza & kebab place right next to these bars. The service is poor, you often don't get what you ordered, the kebab meat is defrosted in a microwave, and the pizzas have about a quarter-ounce of toppings on them. Also, there's a chance of food poisoning. In a word, don't.
Vanha Pankki
(****)
This place used to be a bank, as the name says. It has a fairly pleasant pub-type atmosphere, although sometimes the old hard-drinking laborer types present can be a bit unsettling. There's a jukebox with a fairly good selection of all kinds of music, downstairs you'll find a pool table and dart board, and in the summer there's an open-air terrace.
Food orders are taken until 11pm. The burgers are rather good, and come with a token salad. All prices are entirely reasonable, and on Wednesdays a variety of Happy Hour starts in the afternoon and goes on until closing time, an hour or two after midnight - the beer is priced pretty much the same as it is at the grocery store. Yours truly and some of his friends tend to be around on Wednesdays, they'll be the bunch of hippies, goths, and miscellaneous.
Except for aforementioned goths and hippies, it's not much of a place to strike up conversations and meet people. Go with friends. The location is fairly out of the way, a good ten, fifteen minutes' walk from town center. Head out of town towards Kivisakasti, the medieval chapel, and turn right immediately after passing it. Go up to the top of the hill, and Vanha Pankki is on your right.
There is no bouncer. There are no lines, ever. There is no coat check fee.
Handy notes for those not familiar with Finnish bar culture: A beer is .33l, roughly 3/5 of a pint. A large beer is .5l, just under a pint. Shots are 4cl, more than half again the regulation size in the UK. Drinking age is 18, legally mandated closing time is 3:30am.