Some are described in the man page. 
* (DONE)However one thing that I highly desire but unable is to release a FreeBSD version of mGet (given that I donot have any FreeBSD machine in my access and my institute internet connection passes through a firewall and stops me from telnet-ing to outside machines :( ).
* Stop downloading at some point keeping some log file and later resuming it. Working on it.
* Given a list of URLs for the same file, get files from each of them.
* Stop the wastage of 1st thread i.e. use to download some data rather than just getting length information.