I have a bunch of scopes, not all are the "best," not all are the "worst," but I'll give my input on the ones that I'd buy again. Some other models I'm happy with, but I wouldn't necessarily buy them again over any of the models on this list.
Under $100:
Bad:
Barska. I've had two Barska's in this price range, both regrettable purchases. One is a 6-24x50mm AO "Varmint" model that I bought for $89, the other a 1.5-4.5x20mm "Tactical" model that was $115 when I bought it. I've wasted $200 on dumber things, but these are close to my worst investment ever. Very bad light transmission, inconsistent click tension (you might make 3 clicks and not feel or hear them).
Good:
Bushnell Banners. I have a handful of them, and they're all good scopes, but "great scopes for the money." These are getting hard to find under $100, but I have a 3-9x40mm Banner that has made the rounds on different rifles as a "spare scope" for several years that has been zeroed and rezeroed many, many times, and still holds zero. It's taken several deer to 300yrds, and made a brief tour on my wife's 45-70. Surprisingly good glass for the money - built exactly as it should be: These are good optics without the bells and whistles, not crappy optics with fancy features to lure you in (like the Barska's above).
Even though I have a couple other NcStar products that are complete schitt, I have to tip my hat to an NcStar 3-9x40mm that I have, a $49 scope. Other than the weird blue tint caused by the orange mirror objective lens coating, it's surprisingly clear with good resolution and light transmission, and tracks very well for adjustment. I bought it on a bet that it wouldn't survive the recoil of a 44mag with a local gunshop, which I lost. It rides on one of my 10/22's these days. No frills, and nothing spectacular, but for $49, it's probably the best bang for the buck I've ever gotten in a scope.
$100-300:
Bad:
Tasco High Country 4-16x44mm. I've had this scope for almost 20yrs, and it has been a fight since the first day I bought it. Seems like I paid $250 for it back then. It holds zero well enough, and I took a lot of game with it over the years on my .30-06, but it's a really terrible scope. Fogging and glaring have been an issue since the beginning, and resolution is awful. Light transmission has been terrible. All of that adds up to a pretty wicked headache if I take more than 10-20 shots out of it at a time.
Good:
Bushnell Elite 3200 Series. I have Bushnell Elite 3200's in 3-9x40, 3-9x50, and 4-12x40mm, plus one in a Pistol Scope in 2-6x32mm that are all very bright, reasonably good resolution, solid zero, all around dependable and functional scopes. Same concept as the Banner, but a little more refined - good glass without the frills.
Bushnell AR 3-9x40mm. These aren't at the top of my list, but they're proving to be a good scope for the money. I recently picked up 2 of the Bushnell AR 3-9x40mm scopes, and have been happy with them. I'm not sure that they're "better" than the Banners, and they're certainly not up to par with the Elite 3200's, but for the $150 I have in them, they're good scopes. The exposed turrets come with the consequence that you might accidentally adjust your scope without realizing it in transport, but the turrets are resettable and the markings are clearly visible to make sure they're zeroed before your shot.
Nikon Buckmasters (includes Coyote Special and "Active Target"). These are actually discontinued, but there are lots of them out there as old stock, tons of them on the used market, and the "Active Target" scopes are still available as production models it seems. There seem to be two classes of these, with the SF's being a bit higher quality than the fixed parallax BDC models. I have Fixed Parallax models in 3-9x40 and 4-12x40mm, and Side Focus models in 4.5-14x40 and 6-18x40mm. True to Nikon form, they take a bit of focusing to eliminate edge effects at high magnification, but they're very clear with great resolution, very good light transmission (hard to beat Bushnell for lighting though). They do what scopes should do, for $250-400. The BDC models have been on closeout for some time at Cabela's, bouncing back and forth between 25-50% off, so I got my 3-9x and my two 4-12x models for $129 and $149 respectively.
Leupold Rifleman 3-9x40mm. Gotta give Leupold their due in this range. I tend to lean towards Bushnell or Nikon over the Rifleman line, but I have a 3-9x40mm that's a great little scope. Better than the Bushnell or Nikon? Probably not. But it does say Leupold on the side - which matters to me since it has a lifetime transferrable warranty, and I bought mine used. I'm breaking my rule here, I'd probably buy a Bushnell or Nikon over another Rifleman, but it's still a good scope that earns a recommendation.
$300-500:
This is kinda a no-man's land for me. I either tend to spend a little or a lot, and this gap is right in the middle.
Bad:
I've been lucky enough - or smart enough maybe - to not end up with any lemon's in this price range.
Nikon Monarch - Old model high magnification. The only $500 scope that I've purchased that I was not happy with has been a Nikon Monarch, which I can't recall if it was a 6.5-20x or a 6-24x. I bought it as a long range scope, only to find out that it had a paltry 20MOA internal adjustment. For a 308win mag that I was mounting it upon, it didn't have enough adjustment to get me 1,000yrds, even with an angled base. It seems that the new Monarchs have fixed this issue, but it's definitely something that I consider before I drop a dime on a scope these day - Lesson Learned.
Good:
I probably wouldn't buy another Vortex Viper HS scope, but that's more out of personal preference than any real performance lag. I have a 4-16x44mm that is a very good scope, but for the $450 price tag, I'd buy something else next time. So I suppose that should go in my "bad" column, but it's not a bad scope. But I'd buy something else.
Leupold VX-2's and some of the VX-3's tend to fall in this ballpark. For me, if I'm going to spend $500 on a scope, I'd tend to lean towards a side focus, or at least adjustable objective model, so I'm willing to spend more. I have a VX-2 with AO that I think was just under $500 that I like a lot, but in general, I find myself spending more for a step higher scope.
$500-1000:
Leupold VX-3 LRT 4.5-14x50mm with custom shop Mil-Dot reticle for around $1000 has become my favored glass for all hunting these days. My wife and I have started replacing these onto most of our hunting rifles. Great magnification range for my style of hunting, great light transmission with minimal distortion, great resolution, rock solid tracking, and minimal backlash in the side focus adjustment.
$1,000+:
Good:
Nightforce NXS 5.5-20x56mm and BR 8-32x56mm. You'll pay a lot for the difference between the NXS and the BR scopes - which for most folks, is only the difference in adjustment speed between an AO and an SF. Hard to beat for their FOV and magnification, even at that price point. Nightforce really got a foothold by weighing less than the US Optics that used to dominate the firing line, but they've definitely earned their reputation. Some folks struggle with adapting to the FFP reticles, but it's great if you use your reticle for ranging.
Zeiss Conquest 6.5-20x50mm Old model. It was a little short on internal adjustment, but the clarity and resolution was spot on. Tracking was solid, overall very good scope for the money. I suppose I'm breaking my rule again here, because I wouldn't buy another one, favoring the Leupold VX3 or the Nightforce NXS, but my wife was very happy with it.