Plan B for spy (What spy revolver?)

Lets weigh the different options:

• Revolver / Big Kill - Standard damage. Kills lower HP classes in 3-4 non-crit hits.
• Ambassador - Lower damage shots, slower firing rate, no random critical hits. Headshots do 102 damage if you haven't fired recently... you can tell because the firing reticule in the center of the screen will be at its smallest size. Kills lower HP classes in 2 hits if one is a headshot, otherwise 4-5 hits.
• L'Etranger - Lower damage shots, recharges cloak on hit. Kills lower HP classes in 4-5 non-crit hits. Extremely useful when being used with the Dead Ringer... less so, but still somewhat useful with the Invisibility Watch or Cloak and Dagger. Also part of the Saharan Spy set, in case you want the silent decloak set bonus.
• Enforcer - Higher damage shots, cloaking takes half a second longer. Kills lower HP classes in 2-3 non-crit hits. Extremely useful with the Dead Ringer, where the downside doesn't apply.
• Diamondback - Lower damage shots, no random critical hits, gets guaranteed critical hits from backstabs or when your sappers destroy buildings. Kills lower HP classes in 4-5 non-crit hits or 2 crit hits. Unless you're fighting mini-sentry Engineers, this gun is largely inferior to all the others.

These days, I tend to flip between using the Enforcer with the standard Knife/Dead Ringer and the L'Etranger with Your Eternal Reward with any cloaking device (and Saharan Spy set). Occasionally, I'll use the L'Etranger with the DR and standard Knife or the Saharan Spy set with the Dead Ringer.

In terms of pure damage, if you have time to aim, the Ambassador is your best bet. If you can't, the Enforcer is. If you tend to run out of cloak a lot, the L'Etranger can help, but remember that you break disguise when you shoot enemies with it.

In my personal experience, the L'Etranger seems to miss more than the other guns. All revolvers shoot straight down the reticule for the first shot, but somewhat randomly for successive shots until they cool down. This is much easier to tell on the Ambassador, as the cooldown is identical to the headshot cooldown.

Having said that, if you have auto-reload on, the reload animation takes slightly longer than cooldown, so letting it autoreload and complete the animation is another good way of telling if the cooldown is done.

I usually roll with the Ambassador.

L'Etranger is only really useful when you're on a map without much metal (such as 2Fort) as it's not particularly useful in combat (I also find it hard to hit with, negating its usefulness even further). Oftentimes its just simpler to wait an extra few seconds, or pick up some metal / weapons (perhaps from the poor fools you just stabbed?).

Ambassador may do reduced damage normally, but one crit headshot followed by point-blank bodyshots (since you can only fire dead-accurate shots slower than the normal refire time) can kill an otherwise stab-safe sniper who's using the Razorback.

Regular Pistol doesn't have any real advantages, and is strictly middle of the road. It's best if you play "Revolver Spy", but if you're playing "Revolver Spy", perhaps you're playing the wrong class to begin with.

Even though they have rather different stats, all the Revolvers can be useful in my opinion.

Regular Revolver is overall average, since its fire-power is alright, but not to be used as a focusing weapon. I say use it as a last-resort weapon when finishing off foes from a distance.

Ambassador is a trade-off for accuracy, so it's nice to use if your a good shot. The kind of situation you could use it in is a possible cornered situation (something similar to a Revolver situation).

L'Etranger kind of feels like a gimmick weapon in my opinion, due to the cloak boost being the only real perk of it. I suppose that's not really a bad thing, since it can be used well (just not often from what I've seen). You can use it to get back your DR and IV charge back, so at least it has that.

Enforcer would most likely be better used a finish-off weapon because of its DPS increase for killing off enemies. The slower firing speed doesn't really effect the perk of this weapon from what I've seen.

Diamondback should be useful for Gunslinger Engineers, with their low-health Mini Sentries. As for Regular Buildings and Sentries, I suppose it can come in handy with the Stock Sapper. Relating to stats, it's basically the Ambassador minus the Headshot Perk.

Final recommendation: I say Ambassador or Enforcer would be the most useful, but I prefer all of them.