Track pad most of the time but a bluetooth Logitech travel mouse when I need precision. The travel mouse purely because I already had it. The track pad sits on the right of the keyboard but someway forward since I found it awkward when it was right next to it.
Just ordered one of the new 27" iMacs - Track Pad again - should be getting it on Wednesday or Thursday!
PS: I've just seen I'm still a newbie! I've been here since I got the current iMac in june 2011...
I use a Magic Mouse but I wish Apple would design it to act as a Magic Trackpad too. Or even just a tap to click option like carjackester above me points out.
I would really love an all-in-one hybrid Magic Mouse/Trackpad from Apple next time they redesign their input devices.