TinyWarz.
First off, this game is fun and the person who made it and maintains it seems to be a decent guy trying to keep an indy MMO in the black in a world were that isn't generally believed to be feasable. Indy MMOs are things you spend money to make, not something you normally make a living on. I enjoy killing bandits for XP, mining ore and cusomising my fleet of battlemechs.
Then the downside.
Registering this game will cost you money. There are measures in place to ensure you don't find out how much until your credit card is in your hand. I spent an hour trying to find this information and it doesn't appear in any of the FAQs of help files or service pages. Presumably if one where to click on the buy Tinybucks button, one might be told the price.
Moreover, Registering is called purchasing Paid Days, which can be done with Tinybucks which are bought with real money or earned in small increments by getting other players to sign up and buying products that the site advertises.
The name paid days implies that this is less of a registration fee than an ongoing service fee, but once again, detailed information in unavailable with a consistency that seems to imply deliberate misinformation.
Edit:Found the information!
Tinywars will cost you about $4 a month to play past level 5 if you buy in 30 day increments. However, if you buy 360 days at a time it costs about half that, $24 a year. That's a hard price to beat, until you consider that booster packs of blueprints will also cost you real money, unless you buy from other players in-game.
Construx packs go from $2 each down to 1.50 each, if you buy 32 at a time.
For the sake of completeness!