Smith-Corona SUPER 5 Series (sometimes called "1950 line")

Effortless, parallel key action removes finger and hand fatigue.  Useful touch regulator helps adjust for strength, speed.  Comfortable keytops.  Highly refined control location and operation, particularly on carriage.  Very reliable; easy to repair.  Ribbons available everywhere.  Rugged carrying cases, especially the later hard-shell Holiday Case.

Many models, differing in features.  SILENT-SUPER, the top model is shown.  SUPER is similar; two less keys (some SILENT-SUPER also two less keys.)  SILENT similar but manually placed tab stops; other models such as STERLING and CLIPPER with even fewer features (ie tabulator, paper support arms) but same mechanism and typing feel.

One of the best typewriters of any kind ever made anywhere.
The Smith-Corona SUPER 5 line is our best pick for any typewriter you can buy today and use.  This goes for any size, any year of original manufacture and any place of manufacture.  The Super 5 is properly a large, heavy portable - and there are many other machines out there, even heavier and larger and very much smaller and lighter, which you can buy today.  We will break up our picks into rough size groups for ease of consideration.  Assume nothing about machines not shown -- we cannot review EVERY typewriter ever built!
Corona / Smith-Corona SPEEDLINE machines, made 1938 to 1950 are good machines and largely like the SUPER 5 in a number of ways, particularly key action, but the refinements of the later Super 5 series edge the Speedline out.  We still recommend the Speedline machines.
Later Smith-Corona machines, like the GALAXIE at left (this lineup was first introduced 1959) are also decent enough machines, but they are not as good as the Speedline 1938 machines are that puts them two steps down from the Super 5 line of 1950.  These late machines (made through the early 1980's) tend to have lower quality, and can rattle quite a bit.  They do in some cases have interesting features (some machines, for example, have a special paragraph indent key) but these don't make up the difference. 
In the range of small, flat travelling portable typewriters the Smith-Corona SKYRITER is one of our top picks.  They are readily available, reliable, easy to use, very light, and fairly fast.  Nothing likely to get out of order.  Same comfortable keytops as Super 5 line.

There are earlier machines in this line (ZEPHYR) and later ones (CORSAIR, COUGAR, COURIER) but we cannot recommend the Zephyr as highly as the Skyriter although it's acceptable and do NOT recommend any of the later, plastic-bodied machines mentioned.  The very late Courier / Courier CT are in fact particularly bad typewriters.
There are a number of good reasons for Smith-Corona portables from the post-war period to be on the top of our list that are operative, but it should also be recalled that they are very plentiful (they sold in large numbers, and stayed working) and that there will probably be a large supply of the machines and parts (they can't all survive intact) or else replacements.  However, there are naturally other machines we can suggest -- but remember we can't suggest really excellent machines that you cannot find.  One example is the ALPINA -- these are incredible typewriters, but they're so hard to find in the US that searching for one can prove fruitless for a year or more even with e-Bay.  Thus, we'll leave unfindable machines out of the listings and recommend machines we find acceptable that you should be able to find.
We highly recommend the post-war OLYMPIA machines, such as are shown here.  These are in the SM model series, running from SM3 through SM9.  Keep in mind that machines such as the top three shown here are carriage-shifted, not segment shifted and these require stronger hands (and little fingers.)  All are capable of good speed, are reliable and comfortable to use.  Many people prefer these to Smith-Corona machines; there are enough variants of both kinds (Olympia, Smith-Corona) to make model-for-model comparison confusing and rather invalid. 
The little, flat OLYMPIA SF series as seen at left is among the very best of the small, travelling machines and is very highly recommended.  We like this machine as well as we like the Smith-Corona SKYRITER.  Available in a variety of model names which actually do not differ significantly enough to warrant complete discussion. 

Do not be fooled by OLYMPIA machines made in Japan.  They are unrelated in design, even though obviously the same company ended up marketing them.
The HERMES 3000 desk-model portable, manufactured in Switzerland by Paillard SA is a good machine, whether in the older round style as seen at left or else the squared-off later style below.  We cannot make this a top pick because of the sheer awkwardness of the controls all over the machine; too futuristic, and trying to hard to re-invent the wheel.  Still, they work smoothly and fairly rapidly and are recommended.
A very highly recommended machine is seen here.  For a short while during the 1960's Brother, of Nagoya, Japan made a large and heavy portable in addition to its usual range of small ones.  The large machine was a totally unrelated design, vastly superior and probably too expensive to continue.  These can most often be found in the USA carrying the Montgomery Ward brand name SIGNATURE and will have model numbers in the 500 range.  This machine is a SIGNATURE 510.  They are notable for parallel key action, very solid construction, well thought out controls all over, a novel pushbutton ribbon selector in some models, a really good touch regulator, and more.  Unfortunate that these didn't do better.
The small, travelling machines by Hermes, such as the Hermes Baby (at left), the Hermes Rocket, the older Hermes Featherweight and Baby Featherweight are all good buys in the flat machine category.  We like them, although not at well as the Olympia and Smith-Corona machines.  However, this is mostly personal preference (the carriage controls seem awkward on the Hermes machines for example) and the Hermes machines are plentiful and reliable enough to recommend.
Brother produced a smallish machine originally, which was about the size of the Skyriter and Olympia SF or just a bit larger.  It was, however, a bit heavier and certainly felt more substantial than its size would indicate.  Later, this machine was fitted with more options and a rounded top cover as seen here on this Western Auto WIZARD TRUETYPE.  This round-topped BROTHER style of machine is our favorite in the medium-size category.  This category is difficult to represent since many of its occupants are very nearly impossible to find in the US today (for example, the ABC / Cole-Steel and also the Princess and related Maritsa machines are in this size class, but unfindable.)
Further round-topped BROTHER machines.  Some have repeat spacers.  Above Webster XL-747; on the right, Webster. (No model number.)