Irregular lot sizes?

I was wondering which brokers other than Oanda allow you to buy forex at irregular lot sizes? Oanda's java platform has a function that allows you to use your full margin at any time in a trade (I believe this is how magellan of the '55000% in ONE MONTH' thread worked) which means that compounding of profits is constant with every trade.

Also, if a broker that uses a platform with MT4 or similar?

thanks