If you are looking for a market maker and you are also looking for lowest spreads, then the answer can be only Oanda. It has variable position size, fractional pips, continuous interest payment, fast execution, reasonable slippage. Perhaps most imporant, it is probable the largest non-bank forex broker on market (from what I know it is larger than FXCM). It is probable that many don't know that because they don't have a strategy of aggresive marketing by using promotion and introducing brokers. Rather, they chose to build their reputation by providing excellent services to existing customers. And unlike many other brokers, they have a reputation of being fair.
Oanda enables almost all trading styles - from carry trading, positional, swing, day trading, intraday trading, very short term trading and even scalping. It is perfectly ok to stay 5 seconds in a trade. The only style of trading that they cannot provide support for is sniping (arbitraging based on platform delays).