There are lots and lots of options in the market place. Naturally, the Boss OC-2 is the gold standard because it's the original and Boss got SO much right with this pedal. Unfortunately, there's a lot wrong with it too. It's got a weird buffered bypass, it doesn't like hot inputs and there's some gain drop issues with the pure wet octave. Also, no one uses the oct-2 on bass and the dial in is pure analogue so you have to twiddle a fair bit to get the different range of tones out of it.
Then there's OC-2 clones, like the MXR, 3 leaf Audio and COG offerings, all great and all trying to keep the core tones but dial out some of the irritating issues.
Then there's a whole bunch of brand specific Octavers that do their own thing or take an OC-2 and apply a hefty set of baked in EQ's the make a brand specific sound. Some even use a totally different circuit design to get their octave sound. Foxx, EBS, Eden, Markbass...the list is numerous.
Then there's the digital octavers (often including harmonisers). EHX Pog / Hog2, Digitec Wammy, Eventide Pitch factor / H9's etc. These effects sound different to the analogue pedals and can usually track better while also offering polyphonic tracking. They usually offer a plethora of octave up, dual and octave down, plus harmony options. Pure wet, they sound very different and have their specific uses.
Then there's a last last and newest category of octavers, the "digital but want to sound analogue" octavers. To my knowledge there are only a few of these currently. Source Audio own this category with their amazing Spectrum Filter and C4 offering and recently Boss entered this field with the new Boss OC-5.
So you are welcome to draw on this list and choose what's best for you. Personally, I most used octaver is the Source Audio C4. For me it nails the OC-2 totally and I have 3 other voices to add to that. I have midi control, expression and a lot more too. I also have an EHX Hog2 under my board (literally) that allows me to tap into some of the unique features / sounds that panel offers. I also have a pair of Eventide H9's...so that's got all the harmonizers, pitch shifter, octavers anyone could want from a digital math based pedal.
Does any one pedal cover most of this list...yes the SA C4, but it's a broad list and some people like a few click on / off pedal sounds, while others like to call up patches via a Midi controller.