User interfaces and ergonomics are interesting to me--How little thought is given in some cases, how much in others.
I have a bunch of wireless speakers, made by Recoton/Advent. Several different designs, but all share one simple layout flaw--The volume and tuning knobs are identical and side by side. It is very easy to re-tune the speaker instead of changing the volume. It would have been simple to merely change something on one of the knobs, to make it more distinct--make the volume a different color, or with a different texture, or recess the tuning knob.
My work-issued phone and my last PDA have chargers that are semi-symmetrical--They will sort of fit two ways, but will only completely click in one way. A simple raised ridge or dot on both the gadget and its charger would be a vast improvement.
PS/2 keyboard and mouse connectors (the round ones before USB took over) have two problems--The jack is round, but only inserts one way, and the connectors are physically identical but incompatible. Laptops often had a single jack that could do either--Would have been great for desktop machines to have two jacks that would work that way.
My GPS has no "debounce" in its touchscreen--if your finger bounces and touches twice, the system counts it as two clicks. It would have been simple and sensible to ignore clicks that are less than about 1/4 second apart.
My alarm clock has one big button for snooze, and a curved row of 5 identical small buttons for setting the time and alarm. The button you will use most often (to turn the alarm off) is button 4. Why not make it distinct--either the first or last, or give it a texture, or move it out of this row completely?
One of the most ironic is Jakob Nielsen's site. Basically a blog on usability, but without an RSS feed, so you can't see it in a feed reader.
Blogger's date is annoying--it counts when you start a post, not when you finish it. I tend to get a post about 3/4 done, then come back days later. About half the time I have to go edit the date.