All of the gear in Splatoon comes with one static ability and one or more randomized abilities. The only way to unlock the other abilities is to play more matches with that particular piece of equipment. Items of clothing with more stars come with more abilities.
Abilities can stack. For example, if a player has two items of clothing with defense up, then the player receives even more of a defense bonus.
As for which abilities are best (only the default ones, remember the rest are randomized), it really depends on each person's playstyle. Some players will rely more on bombs, while others may use their special weapon more often. Pick gear with abilities that match your playstyle... or just stock up on defense if you can't decide.
- Bomb Range Up: Makes bombs, Point Sensors, and Disruptors travel farther when thrown.
- Bomb Sniffer: Reveals traps and hidden bombs place by your opponent.
- Cold-Blooded: Shortens the effect of attacks that let enemies track your position.
- Comeback: Boosts some of your abilities for a short time after respawning.
- Damage Up: Increases damage of all your weapons.
- Defense Up: Reduces damage taken from all attacks.
- Haunt: Reveals the position of any player who splats you to your team for a short while.
- Ink Recovery Up: Increases ink tank refill rate while submerged in squid form.
- Ink Resistance Up: Reduces damage and movement penalties incurred whe moving through enemy ink.
- Ink Saver (Main): Decreases amount of ink consumed by your main weapon.
- Ink Saver (Sub): Decreases amount of ink comsumed by your sub weapon.
- Last-Ditch Effort: Boosts ink recovery rate and weapon ink efficiency for the last 30 seconds of battle.
- Ninja Squid: Leaves no trace while swimming on inked ground, but reduces swim speed slightly.
- Opening Gambit: Boosts your speed in both Inkling and squid form for the first 30 seconds of battle.
- Quick Respawn: Decreases respawn time after being splatted.
- Quick Super Jump: Increases Super Jump speed.
- Recon: Allows you to see the opposing team on your map while standing on your spawn point.
- Run Speed Up: Increases movement speed in Inkling form.
- Special Charge Up: Increases special gauge refill rate.
- Special Duration Up: Increases usage time of special weapons.
- Special Saver: Reduces special gauge decrease after being splatted.
- Stealth Jump: Hides your Super Jump landing points, but also makes your Super Jump slightly slower.
- Swim Speed Up: Increases movement speed while swimming in squid form.
- Tenacity: Fills special gauge automatically if your team has fewer active players than the enemy.