The Romans and the English queens stand out in my opinion.
Augustus: Whipping discounted settlers into discounted wonders is very helpful on high levels; otherwise spamming wonders in one city for maximum GPP is going to be tough without neglecting expansion.
The forum will have enough early GPP to do something, Praetorians being very long-lived is very useful if your focus is on wonderspam rather than conquest (and they're strong enough that you can play a convincing military game if you desire).
Julius: ORG/IMP and Praetorians will allow a large empire early on, peacefully or not. ORG makes high-upkeep civics more attractive, and a disincentive to run Pacifism makes the forum more relevant. ORG also does more for specialist-happy economies because of more/bigger cities, again giving the Forum more to work on.
Praetorians have enough raw power that half of a military trait (IMP) is enough, and you'd rather have something to speed up initial expansion and somethign to help the economy. ORG puts other economic traits to shame if you're expanding/conquering as fast as possible, especially the latter: If you're cranking production up to 11 (Praetorians, essential infrastructure in newly-conquered cities) other economy traits do little.
Elizabeth: PHI/FIN is great for an uncompromising techer who is willing to postpone expansion/warfare for a bit. A good way to translate this into a win is a Renaissance/early Industrial war pitting Riflemen and/or Cannons against Longbows and maybe a few Musketmen. The Redcoat extends the window of opportunity: while the true fun is over if the AIs get their own Rifles or Grenadiers, England retains a considerable advantage and can mop up easily unless you face mass cannons in time (unlikely).
Last not least, the Stock Exchange synergises very well with a Financial civ - cottages and windmills for rushbuy everywhere, no production improvements in most cities.
Victoria is similar but less extreme, and has more of an incentive to expand early.
Note: Imao the forum still sucks despite some synergy with the leaders. Irrelevant for this topic. I didn't mention Huayna Capac despite being an excellent leader because his advantages stem from raw power rather than synergy.