A BIG YES! The A/O is cirtical unless you want to readjust your scope either yourself [can be done] or by sending it in to the factory to be readjusted for 50yrds (the standard target range for 22lr). Yes, you can shoot, and be accurate with a 22lr at 100+ but............you're probably going to be at 50 or less yards for most 22lr hunting, plinking, etc.
Nearly all "rifle / hunting" scopes without an adjustable objective [A/O] are set to 100yrds from the factory. A rimfire rifle [22lr] has an "optimal" or "common" range of 50yrds or less. For shooting at less than 100yrds, you WILL need an adjustable objective to correct for parallex. (parallex, is a whole can of worms - do a search for a definition of parallex, or maybe someone better at explaining can breif you here...) In short, parallex will throw off your POI (point of impact) at distances greater or less than that of the setting. If you have an adjustable objective, your accuracy can be GREATLY improved upon by simply adjusting for the correct distance at which you are shooting thus, adjusting to correct parallex. Basically, it will just give you a MUCH more versatile and accurate scope if you are concerned with accuaracy, which I assume you are being you want a scope in the first place.
As far as the most rugged........hmmm......the only thing I can really think to tell you there is both the Simmons 1047 and 1048 as well as the WTC18 have a "Black Granite" matte finish (scratch resistant, not gloss blued.....
The Weavers we mentioned are both "Matte" and I suppose scratch resistant.
Not sure about the "Rimfire" and "22mag" models that BigMike mentioned......havent seen 'em.
As far as holding a zero, I'd say that falls into the whole quality issue.....I'd bet that all the previously mentioned scopes perform fairly equally in that regard.....they are all very good quality scopes. So far, even my super cheapy Bushnell Sportview [bought for $30 bucks a few years ago] has held a zero on my airgun. It just kinda depends on what you get I suppose......again, for this issue, and many others, I'd still say you would be safe to stay away from Chinese optics.
BUT GET THE A/O!!!!!!
