I honestly cannot think of a better nightlife spot in Sweden. The famous Tylösand Hotel is these days co-owned by Roxette's Per Gessle which means it's all about fun and music during the long summer nights. On top of that, the hotel is right next to the beach and so, you can find your own sand dune for that flirt, or go for a swim with your friends if you're not too drunk. Best is Bettans Bar which is the part of the hotel closest to the beach, with a bar opening up to the sea. Then there is the downstairs bar with loads of Roxette's silver and gold albums lining the wall in the bar where the pillars are scribbled full of cocktails with exotic names. In between, there is a stage where famous Swedish pop artists sometimes perform and if not, be sure there is music (the hotel rooms face the other way). This is the place for fun :) If you want more daytime images, have a look at my Tylösand page.
Dress Code: Decent.
Halmstad city centre is one big nighlife spot during summer when it comes alive, and even in winter there is enough to keep you busy for a weekend as long as you don't plan on Sunday night being included. Storgatan and Lilla Torg are the centres for all action, with loads of pubs and nightclubs. Having a university college, there are also students to liven it up during term time, although don't ask me where they hang out.
Dress Code: Various but decent.