In my opinion:
A300-600 (either version) great aircraft, fits a decent niche, shares maintenance with A310 making operating both a breeze. Also the long range gives great ability to expand.
A340, the entire family. A340-300 is a great replacement for the SP and has an unmatched range until the 777-200ER. A340-500 offers crazy range while slotting into the A330 maintenance cost, and again is unmatched range until the 777-2LR. A340-600 is alright, its not great but not terrible.
BAE146/Avro RJ. I have seen people sleep on this regional jet, and that's sad because its got incredible short field performance (It is the last jet you can buy that can land at Toronto Billy Bishop until the A318) and is decently sized with good range.
Likewise, the CRJ series often lands here, especially the 200 and 100. While the base CRJ-200 isnt great, the ER and LR are pretty good, and can operate some skinny routes that any other aircraft wouldn't really be able to.
The A321-100. Sure its got short range, but it is really helpful on shorter, higher demand routes.