I don't think I can pick one.
This is probably what I use each one for the most, though.
EMS (electric mandrel spinner) invaluable to me for getting even beads and quick shaping.
Graphite marver (smooth, does not "stick" to the glass)
Brass stump shaper (seems to "grab" the glass more. helps to move it around better - and is a better heat sink to help push dots or stringer designs into beads)
Tungsten pick (I use this to actually stick into the hot-soupy glass and move it around for organic designs)
Corina Magic tool (although I could substitute a razor blade tool if I had it) (puts lines into beads, cuts lines into gathers to make small murrini, makes creases)
Stainless pick (I use this instead of tungsten to actually rake the glass because it grabs the glass a little and pulls it around better. Use for pulling only, or it can get stuck in the glass. Some folks use little glass stringers for this job, but these are easy to make from old mandrels, and work better for me).
Cattwalk crunch presses. Great to get flattened beads that have a gentle curve to the outside edge. I started with the standard size, but probably use the long and lean one more.
The Kote (a long steel paddle) looks like if you got used to it, you could do lots with it. It's long enough to use as a good marver, it's got edges that are sharp enough to do creasing with, and they aren't pricy. I just haven't been able to get used to using it.
My suggestion, try one basic one, and plan to set aside a little money every month to add another tool or two. With the exception of the EMS (that I got originally for pain in my thumb), none of these tools are outrageously expensive. $15-~50.