I must admit when I first started playing this game I favoured the sniper but quickly got bored. The laser target is extremely useful but being a one hit wonder it's rather restrictive..
My favourite
Engineer
Pros:
1. I can repair my own vehicle, my team mates vehicles and repair/use abandoned heavily damaged enemy vehicles.
2. Rocket launcher is a very nice weapon
3. Shotgun is handy for slightly laggy people like myself (thanks Orange broadband).
4. Mines - *drool* When someone dies to one of these puppies they take it personally, I've had so many nice fights with the same people coming back again and again to try and break through my defense. Lots of fun! and I usually die horribly!
5. *Rarely* but I have had people stop and let me get onboard to man a gun after going past several snipers who they know will abandon them at the first chance to get a sniping spot.
Cons
1. Rocket launcher is slow to load and only 5 shots before your looking for an ammo cache.
2. Shotgun is quite slow firing and restrictive range.
3. Number of times I've been run over when repairing my vehicle and someone nicks it.. (from my own team!!).
4. Snipers love shooting me.
5. You will kill your own team now and then with mines (because they're not looking where they are driving!!) and be at risk from getting kicked
Least favourite:
Sniper
Pros:
1. Excellent killing power with that damn sniper rifle
2. A good sniper can seriously frustrate half the enemy team, people really REALLY take it personally if a sniper keeps taking them out.
3. Laser target is fantastic for taking out vehicles
4. You can drink tea whilst camping your spot
5. Sometimes you just want to be mister sneaky!
cons:
1. It's boring, who wants to drink tea!
2. The pistol although adequate is extremely weak
3. If you lag now and then (like me) you'll miss a heck of a lot of shots which your sure should have hit home.
4. Laser targetter is a one hit wonder.
These are only my personal views and I probably missed a LOT from the pro/con lists. I love my engineer, if I was to rate all of the classes favourite >least favourite it would be:
Engineer> Assault> Spec ops> Support> Sniper
My favourite
Engineer
Pros:
1. I can repair my own vehicle, my team mates vehicles and repair/use abandoned heavily damaged enemy vehicles.
2. Rocket launcher is a very nice weapon
3. Shotgun is handy for slightly laggy people like myself (thanks Orange broadband).
4. Mines - *drool* When someone dies to one of these puppies they take it personally, I've had so many nice fights with the same people coming back again and again to try and break through my defense. Lots of fun! and I usually die horribly!
5. *Rarely* but I have had people stop and let me get onboard to man a gun after going past several snipers who they know will abandon them at the first chance to get a sniping spot.
Cons
1. Rocket launcher is slow to load and only 5 shots before your looking for an ammo cache.
2. Shotgun is quite slow firing and restrictive range.
3. Number of times I've been run over when repairing my vehicle and someone nicks it.. (from my own team!!).
4. Snipers love shooting me.
5. You will kill your own team now and then with mines (because they're not looking where they are driving!!) and be at risk from getting kicked

Least favourite:
Sniper
Pros:
1. Excellent killing power with that damn sniper rifle
2. A good sniper can seriously frustrate half the enemy team, people really REALLY take it personally if a sniper keeps taking them out.
3. Laser target is fantastic for taking out vehicles
4. You can drink tea whilst camping your spot
5. Sometimes you just want to be mister sneaky!
cons:
1. It's boring, who wants to drink tea!
2. The pistol although adequate is extremely weak
3. If you lag now and then (like me) you'll miss a heck of a lot of shots which your sure should have hit home.
4. Laser targetter is a one hit wonder.
These are only my personal views and I probably missed a LOT from the pro/con lists. I love my engineer, if I was to rate all of the classes favourite >least favourite it would be:
Engineer> Assault> Spec ops> Support> Sniper