Nomad BT Brickwall BW2S-3

Check out the Sonitus multiband compressor (don't laugh). If you're using the brickwall to squash the sound and get that pop music thang, it doesn't really do the job...Waves L-series stuff is my preference there. But, if you enable the limiting option on the master page, you can push that puppy pretty hard, like +6dB over 0 at the input. The output ceiling is an automatic -0.1dB.
 
Its best use is catching transients, like if you have something that's pretty much ok and you just want to make sure you don't get any overs. 
 
But the ceiling restriction isn't necessarily a restriction...it helps discourage intersample distortion, which can show up when a project hits a duplicator and cause it to get rejected for overs. If you really want to max out, you can render with the brickwall and normalize to 0.01 dB or whatever.

a Pensado's place video a while back had a producer say 'Brickwall limiter' as his answer for Acoustic Guitar. I don't know how valid this is, I've yet tried yet, and those two guys always nod and agree with wonder and adoration with everything producer/engineers answer in those single answer question rounds. 
 
Sorry a little off topic, but just a liittle.

Another vote for ToneBoosters Barricade, also IK's Brickwall Limiter I quite like

I have and use Barricade and  Elephant - still have and occasionally use Kjaehus MP1pro (obviously only 32 bit and getting a bit long in the tooth now)
Just lately have been using Ozone 5's limiter - I never got on with this and although I would use Ozone, I would disable the Ozone limiter and use something else. But lately I think I have finally taught myself how to use it more efficiently!! Like most software I think, ALL / MOST will do the job perfectly well - the problems / perceived deficiencies are normally pilot error!!!!!!
Nigel