MultiSigWallet.sol is the exact verified contract currently storing millions in assets:
https://etherscan.io/address/0x851b7f3ab81bd8df354f0d7640efcd7288553419#code
Use Solidity compiler version v0.4.10+commit.f0d539ae and disable optimizations to get identical bytecode (except for your own constructor arguments).
This repo is the "original" Gnosis multisig wallet written by @Georgi87 and stil in use by Gnosis. For more information, including frontend code, see https://github.com/Gnosis/MultiSigWallet