I have written of them in the past and a reader recently pointed out another one: the McElroy "Junior," a semi-automatic telegraph key built for the ham or telegrapher of limited means.
The base and frame were made of stamped and welded sheet metal and they were the least-expensive bug ever made. They're also vanishingly rare, which leads to an interesting quirk: while you can find a nice Mac "T-bar" bug for about $500 and his high-end models for up to a couple hundred more, the humble little "Junior" sells for as much as -- see for yourself:Yes, that's $1026.01. I did not bid on it; bidding rises early on these and keeps on going up.
I do note, very typical of McElroy, that the inner construction appears to be quite robust and seems to include some kind of additional pivot support; mechanically it is a better key than first glance might suggest.