For a cheap one-night or short term stay, Omena offers a very convenient central location near the Kamppi metro/tram stop and shopping center, with basic amenities, smooth self-check in and self-admission. Do be aware that this is a staffless hotel, so make sure to keep your phone charged and/or the door code written down.
There is also a billiard bar downstairs, open until 5 AM on most weekdays, with occasional rowdiness outside. Probably not the first choice if you are traveling with children, but for adult budget travelers with realistic expectations, it’s good value for the money.
The only issue during my last stay here was that the shower basin was quite slow to drain, and a lack of surfaces to put down bathroom products, which in both cases constitute only minor inconveniences.