Here's a tip for you. If you are one of those people who constantly call the Excel guru over to your desk to help with a problem, ditch the Darth Vader mouse. I can't tell you the level of annoyed I reach when I have to sit down and use a mouse designed for an alien. What is the fascination with novelty mice?
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Here's a notice to you nerds: If your mouse looks like any one of these, don't call me over to your desk.
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The Track Ball
I refer to this as the "Darth Vader" mouse. As soon as I see one of these I know I'm in for some really interesting conversation. Unless you have spider fingers, it takes 16 strokes of the ball to get from one end of the screen to the other. Believe me when I say that if most of these weren't wireless, there would be more workplace strangulations.

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The Free-handed Mouse
Does anything say "I don't do squat at work" better than lounging back in your chair and using a free-hand mouse? My god man, how relaxed can you be? When I see these, I know there is a Workforce Reduction list somewhere with this douche's name on it. When I have to sit down and help one of these guys, I always feel like I'm running a slideshow presentation.

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The Mini-Me
This typically belongs to some jack-ass Mckenzie consultant who thinks it's cool to have a travel mouse. I call it Carpel Tunnel To-Go. One thirty-minutes session with this bastard really does wonders for the arthiritis. Unless you're an oompa-loompa with interesting stories about chocolate making, keep this thing out of my face.

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The Joystick Mouse
This one is reserved for only the most tooliest of tools. Here's some breaking news – pretending to play Atari is not going to make your crappy job any more fun. It's definitely not going to get me to come over and fix your formulas.

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The Glamour Mouse
You typically find the glamour mouse in a cubicle full of Beanie-Babies and plants. This mouse typically belongs to the matriarch who's been with the company for years, but still seems to get confused by technology. They often say things like "I really should invest more time learning the computer."

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The Booby-Mouse
I removed the booby-mouse because it was a bit too creepy.
Hi,
Have you tried one of the new wireless optical versions that are claimed to work on glass table tops?
Have you got an opinion/recommendation on them?
Jim: The places I work aren't fancy enough for glass table tops. My home office has a nice balsam finish. No glas there either.
I have to agree on the joy-stick and the track balls. Can't stand either of them. Then there is the "ergonomically shaped" ones. Even if you can get past the creepy "why does if feeling like I am fondling something" feeling and actually start using it, your hand starts locking up after a few minutes.
Give me a traditional optical mouse any day.
"This one is O.K."
ROTF!!
Those ergonomic mice suck, because they only fit the right hand. I switch mouse hands to reduce risk of RSI, so they are useless for me.
I have been using a "Darth Vader" mouse for a while now and I love it. Never had shoulder or wrist problems ever again. And because you don't need a surface to slide them on, you can use your mouse anywhere. That being said, Jon's point is valid – they are not ambidextrous, which is too bad, because switching is one of the best ways to avoid repetitive stress problems… and I also always have a classic mouse available for the occasional guest!
You forgot the gyroscopic 'air' mice. Also, no bacon?
I'm using a Humanscale ergonomic mouse, which has a base tab that you can use to turn it into either a left handed or a right handed mouse. Hard to explain without the use of graphs.
It also expands to fit the size of your hand. Every mouse should do this.
http://www.humanscale.com/products/switch_mouse.cfm
What the hell is the point of a wireless track ball anyway?
I work with DataPig. It gives me immense satisfaction to know how annoyed he is by my Darth Vader mouse! In fact, I'll start asking for help even more now that I understand the full depth of his irritation.
jeff weir said: "hard to explain without the use of graphs."
Is that what you meant, datapig, when you said "As soon as I see one of these I know I'm in for some really interesting conversation."
Also, as a lefty, I must agree with Jon Peltier, those ergonomic mouses/mice suck, they're not ergonomic for me.
I think it was Sartre who said, "Hell is other people's mouses".