So generally what does the pre pushback brief consist of? I have seen that emergency procedures such as rejected takeoffs are commonly talked about.

This can depend, but its pretty normal for the pre take off brief to cover the expected taxi out plan, the runway, the departure, acceleration height, initial altitude, and any special engine out procedures that may apply. Some additional things may include items such as the previously mentioned contaminated runway, possible wind shear, whether or not you may have to deviate on the departure for certain weather conditions, applicable MEL's/CDL's, etc.

As far as items you've mentioned go, things such as fire, evac, RTO/abort procedures, etc, that's usually covered on the first leg of a trip, and usually the PIC's discretion after that. If he/she if fine with covering it on the first leg, it's usually "emergencies as previously briefed" after that. If he/she want's to cover it on the first leg of every day, or even every leg, again, the PIC's discretion.

Interesting, I would think that having to brief that stuff every time would be a little repetitive especially since the ep's shouldn't change pending any special considerations.

True, you're right. Like I said, it's PIC's discretion to do so. And 99.999999% of PIC's do exercise that discretion. It's been rare that I've had a C give the entire spiel EVERY time. As I mentioned, the take off brief will cover the things particular to that flight, when finished, the usual follow up is "emergencies as previous briefed, any questions?"

Thanks for brining this up, i was going to post this same and caught this

Small on demand 135 operator...not an airline

In many cases, the (not so) brief on the gate includes the departure and any special considerations (runway conditions, wx, reduced thrust). Essentially as much as you can get out of the way before moving the airplane including V speeds if possible. Also, the rejected takeoff. So you can see why the not-so-pretakeoff brief can and probably should be done at the gate.

At the end of the runway, you are left with maybe a rebrief of the numbers if wt/bal has been revised, anything diff from the gate brief, first fix and first altitude.

Agreed
 

Each carrier, whether Part 121 or 135, probably has a slightly different variation of the briefings. The Departure Review can and probably should be done at the gate with a Take-off Briefing, as III Corps said, done just prior to taking the runway.

The Take-off Briefing reviews any changes to the Departure Review, verifies runway, flap setting, thrust setting, T/O weights and V speeds. Also, it's important to review the ENG OUT procedures so that it's fresh in everyone's mind. I would also include the initial portion of the departure procedure with any restrictions; "O'Hare Six Departure, left turn to 270, up to 5,000 with a 3X5 and 4X8 restriction".

G'Day and fly safe and have fun !!:)