Meh, I'm always changing my stuff around. I usually run one of each of an assault rifle, SMG, LMG, and sniper class. I also have a random Anit-Air and One Man Army class.
As for for the AR class in particular I usually run a TAR-21 Silenced, AK-47 or a ACR w/ Red Dot with a shotgun (usually the AA-12 or the M1014.) and usually my equipment is a Claymore since Scavenger Pro begs Claymore hilarity. As for perks, Scavenger Pro is almost always on my AR class as well as Stopping Power/Danger Close (depending on the particular AR) and Steady Aim Pro.
SMG I usually run with a silenced UMP45 or the Mini-Uzi depending on much I'm running and spraying or trying to actually shoot with accuracy. Secondary I usually run around with the USP .45, which is ironic since I typically don't run around the with tactical knife because I hate knifing classes. Equipment is usually the Throwing Knife, except I'm horrible with it. Perks, it is usually Marathon Pro, Lightweight/Cold Blooded, and Commando/Ninja/Steady Aim. I rarely use my SMG class. Usually only on Objective modes that call for it like Capture the Flag or Sabotage.
LMG is usually an MG4 or M240 with Grip (and sometimes ACOG) or an RPD with Grip. Secondary I usually run the SPAS-12, no particular reason except to offset the low damage of the MG4 and M240. Equipment is always changing on this class, usually Semtex because I have nothing better to use, but sometimes C4 as a good counter Claymore explosive. Perks are usually Bling (particularly with the MG4 and M240 if I feel like using the Grip with a sight) otherwise it is Sleight of Hand, Stopping Power/Cold Blooded and Steay Aim/Scrambler. LMG is usually the class I use second to least because I only use it defensively.
SR (Snipe Rifle) usually consists of a WA2000 with Heartbeat Sensor for long ranged sniping matches on Wasteland, otherwise I run with a silenced M21 EBR for short-to-mid encounters, Secondary is usually the M93 Raffica with my WA and a TMP with my EBR. Equipment also depends on the rifle. WA usually calls for me camping more so I use Claymores, while with the EBR I often run around with a tac insert. Perks are usually Marathon/Sleight of Hand (for WA2000) or Scavenger (for M21 EBR), Cold Blooded/Stopping Power and Ninja.
Anti-Air class usually consists of whatever primary happens to suit my whims, but usually an AUG HBAR with Grip, for some reason. Secondary is always a Stinger since it is the best anti-air missile. Equipment is usually a Semtex or C4 so I can quickly kill myself if I'm by myself trying to take down an AC-130 and there are no Scavenger Bags in sight. Perks are Scavenger so I can hopefully pick up more Stinger ammunition, Cold-Blooded and Ninja.
Goto (name I've given my One Man Army class) exists only when I feel like there is a good chance that there will be killstreaks to take care of from the enemy team, so I can quickly switch to my Anti-Air class, which means this class almost never gets used. Primary is usually a TAR-21 Silenced, for whatever reason. No secondary, obviously. Equipment is Claymore since I can easily deploy two with One Man Army. Perks are One Man Army, and second and third tier perks are usually just whatever I happen to be working on or haven't unlocked the Pro version yet.
Wow, that was more detailed than I thought. I try to cycle through all the perks now and again with the exception of SitRep. That perk just sucks. You actually have to make an effort to get SitRep Pro before you end up reaching level 70 and ready to Prestige, it's crazy.
Kill Streak just depends on my mood, but usually consists of UAV, Counter UAV/Care Package, Sentry Gun or E-Drop.
Oh, and my Death Streak is almost always Martyrdom because it is lawl worthy.