As a solo ship the Jag has a lot to offer. It can certainly handle all other frigate sized ships and flown well can be a threat to many cruisers. Basically in this ship you should feel free to engage pretty much any other frigate, assault frigate, light cruisers and interceptors. The only ship that is a real threat is the Ishkur (Gallente Assault ship). The Dramiel is an annoyance as, if dual proped, it can usually run away. I would say that the only real downside of the Jaguar is that most small ships will shy away from an engagement.
In fleet the Jaguar also really shines. Due to its tough tank it excels in the all important task of heavy tackle. There are few other ships that can grab a Vaga and scram/web it long enough for help to arrive. A rifter in this role is usually pulverized within a few seconds.
[Jaguar, Standard Jag]
Damage Control II
Nanofiber Internal Structure II
Gyrostabilizer II
Catalyzed Cold-Gas I Arcjet Thrusters
Medium Shield Extender II
Faint Epsilon Warp Scrambler I
X5 Prototype I Engine Enervator
150mm Light AutoCannon II, Republic Fleet Phased Plasma S
150mm Light AutoCannon II, Republic Fleet Phased Plasma S
150mm Light AutoCannon II, Republic Fleet Phased Plasma S
Rocket Launcher II, Caldari Navy Foxfire Rocket
Small Core Defence Field Extender I
Small Core Defence Field Extender I
Note: In fleet a NOS usually is better then the rocket launcher since it will allow you to hold scram while being neuted.