We see lots of these under different threads.
Talents for Arsenal? Theo Walcott, Carlos Vela, Jack Wilshere, Aaron Ramsey are probably the more notable ones.
Havard Nordtveit is one for the future as well, but he only turns out great if you give him a lot (I mean a LOT) of games - Carling Cup, loans etc. - and with the right training scheme.
Arsenal's best formation without any signings is probably the 4-1-2-1-2, or the narrow diamond. Or if you want to go all-out attack, then it's the 4-2-4 which will only work at the end of the match as you basically have no midfield.
Try these out, come up with your own stuff or look around the site and download the tactics, training etc.