STMicroelectronics has introduced a 250A surface-mount power Mosfet with an on-resistance of 1.5mohms.
The STV250N55F3, is the first power mosfet to combine the supplier’s PowerSO-10 package with ribbon bonding to achieve very low die-free package resistance.

Further benefits of STripFET III include low switching losses and rugged avalanche characteristics. The nine-lead source connection also reduces on-resistance, in addition to aiding heat dissipation. Overall, the package is rated for 300W dissipation at 25 deg C.

Standard driving thresholds also simplify driver-circuit design. The STV250N55F3 is rated for applications up to 55V.

The ability to operate at temperatures up to 175 deg C makes the STV250N55F3 suitable for use in high-current electric-traction applications such as forklift trucks, wheelchairs, and electric bikes. 

Within the same family, ST also has the 55V STV200N55F3, which implements a four-lead source connection and is rated for 200A continuous drain current.

See http://www.st.com