Pretty cool game:
Widget Workshop. Best game Maxis has EVER put out imho. I also have Sim Tower, Sim City, Sim City Resource Editor, I used the Battery Reset program for Depleting the Batteries in the duos, then charging it up. You can have it do this several times to make sure the battery zeros out.
Iomega Zip Tools was pretty good if you had a Zip drive (i have 3, 1x USB 1.1, 1x Parallel, 1x SCSI. The USB is broken) I also used to have an External Jaz drive. So I also used the Jaz utilities.
I also used to use a utility that allowed an FPU to be emulated on Macs that didn't have an FPU (was slow though) I used this on my PowerBook 190cs,
I also used a tool by apple that allowed you to connect an ethernet port up to the serial port, so you can share the ethernet connection, through the computer to the serial, so the serial-connected machine (i.e. a machine with no ethernet) can share the internet connection through the bridge-computer's ethernet.
I used this on my 7200/120 and had my PB 190cs hook up to the internet through it. then from there, it went to a hub, then to the cable modem.
It is availble on apple's site, albeit it's not supported by Apple.
Quickdraw and Quicktime VR are very handy, as well as Quicktime (i used to work with VR Files a LOT)
Also, all the little utilities that apple made for their machines were nice. There was one that allowed you to use the Newton's screen as a tablet input for the apple (through the serial port. then again, that may be 3rd Party)
I believe that was an MP3 player for the old 68k Machines (still, i don't remember the name for it. Just google "68k MP3 Player)
There is also a utility that fools OS 8 into installing on an SE/30 (with the '030 CPU)
Sorry if I don't remember the names, but I am sure with a bit of 'googling' you can find out what they are. I just don't have time to post it right now.