This is just a few thoughts to highlight some skills that I think serve a great group function within Pulp City.
Abilities for Supremes come in a variety of flavours: Traits; Exclusive Actions; Team Powers; Skills. The latter category of abilities covers a range of 'flat' bonuses that always work (unlike actions which often require opposed rolls). Amongst the pretty comprehensive skill list are a handful that have strong effects when team-building, allowing some synergies to be created and therefore exploited for benefit.
Cyberhead - in a team sense this is useful if building any strategies around Mechanical Minions, allowing those Minions to be deployed and used remotely. Plenty of examples including Androida, Chronin, C.O.R.E. (Heroes), Dr. Red, Virus (Hero/Villains), and Mysterious Man (Villain). This is an area the BOOM (Build Our Own Minions) rules can really play on with some work, I feel.
Freelancer - allows a model to 'drop' their usual Sub-faction allegiance; useful for including models such as Sanguine and Kitty Cheshire in Teams led by Dead Eye or Mysterious Man, or to avoid enemy Hatred bonuses.
Greed - a simple skill allowing a cost to be met to allow a Supreme to be used in a faction they do not normally count as; Heroes can play in Villain teams and vice versa with this one. Harrier (Hero) and Gentleman (Villain) have Greed.
Hatred - provides a bonus in opposed rolls against the target of Hatred. Useful if you know potential enemy team composition. Examples include Red Riding Hoodoo, Solar, Nuclear Jones, and Six Feet Under (Heroes).
Leader - boosts starting roll and Action Pool, and stacks with Tactician. Example is Solar using his Exclusive Resource.
Leader of Minions - useful not for the boosts to the team of Supremes, but instead to any Minions brought along to support them. A current example includes Mysterious Man who possesses a very healthy value in this skill. This skill can combine nicely with Gentleman's Team Power which boosts Minions in limited proximity of him.
Merc/Mercenary - a great little skill allowing the bearer to be counted as belonging to the most common allegiance in the team; great for filling out ranks if trying to build an EL 12+ team (in order to use a Level 3 Supreme). Gentleman and Tangent have this skill; Gentleman is great because he also has Greed (above) so can fill out the ranks in Hero Teams (at a price) as well as Villain Teams.
Resourceful - this boosts the available resources, and if choosing a specific resource strategy (perhaps using Minions to benefit from Leader of Minions and/or other abilities) can allow more such resources to be employed of course. Examples include Gentleman, Mysterious Man (Villain).
Super Duo - this creates a binary synergy between two specified characters, providing a small boost based on proximity. A current example include Solar and Stalker (however Stalker is yet to be released).
Tactician - exploit this skill by including Supremes with the skill to boost the AP pool of the whole team. Examples are Trail (hero) and Dr. Red (Hero/Villain).
It is still fairly early in the life of the game, and so the range of available Supremes and therefore abilities continues grow. That said, there are already some great options for consideration when assembling a team, and on balance I have to say that Gentleman remains a great option both for Villains, but also Hero teams (due to his relatively low Greed). Similarly strong Minion strategies could be built around Mysterious Man and/or Gentleman, especially Mechanical Minions.