[juwaack68]

I did a quick search to see if this is already posted anywhere, and the only references to mute/shortcut/7100i seem to point to muting the ringer or the keypad, not when you're on on a call.

I stumbled across a keyboard shortcut to mute the phone when you're using it - the QW key will toggle the mute on/off.

[Nextel User]

BBBA - Blonde BlackBerry Admin
the name suits you. that tip is on the shortcut card that comes with your 7100i from nextel/sprint. it was also posted here in the tips and tricks. BUT its always nice to see again in case others dont know.
the OP key is the speaker by the way.

[juwaack68]

where is it in the tips & tricks? I didn't see i there.....

And there are a LOT of shortcuts that come with the devices, but this site helps out the many people who don't RTFM.