To me, it's more about the performance than it is about the tools. I mean, especially in a studio situation, they (the producer or folks hiring you) usually care WAY MORE about you being able to deliver the goods than what kind of gear you use to do it. There's a very, very high premium on getting the job done right, and getting it done right now.
That said, many engineers and producers are more comfortable when they see gear they're used to - so Strat, Tele, Les Paul, ES-335, Gretch, an acoustic - any and all would make them feel comfortable, as would many close substitutes, like say, a G&L for a Strat or Tele.
In a live situation, ya just gotta go with what you like. I like (GRIN) Les Paul ES-335 Tele Strat
some P-90 axe (for me, a LP Junior or Special)