I love blocking off half the map with guardian / sentry combo. I managed to put 2 turrets guarded by 2 guardians on pretty nasty spots so no one could touch them. As third killstreak I had care package, I got the dragonfly (or whatever it's called) and K9 unit and some other cool ones. They simply couldn't do a thing, I went 66 - 11 and 53 - 9 with kill confirmed (kills/deaths). It's really a lot of fun, but probably less for the opponent team.
What is everyone's favourite setup? This has probably been discussed to death in this thread, but I didn't have the game when it came out.
I just find it hard to ditch the perks that are available from the start by default, such as the Flinch less when shot one. I just got so used to it, whenever I take it off I feel really handicapped.
I also completely ditch any kind of secondary weapon to be able to get an extra perk.
Are there any things that people find, more or less, crucial to equip in this game?
I posted my setup earlier, changed it a little bit, but anyways:
MSMC, quickdraw, FMJ
Lightweight, Hardline (perk 1 with greed perk 1)
Dexterity, Engineer (perk 3 with greed perk 3)
(1x) bouncing betty
care package, guardian, sentry
Playing smart (flanking) is obviously the most important part, I just run around quick, lightweight and dexterity are really important for it. Engineer is very useful if you sprint around a lot, you won't only avoid traps but you can also "know" enemies are there (at least, most of the time). Hardline helps A LOT, there are so many times I am 1 kill short and die. I use one bouncing betty but most of the time I don't even use it. I don't know how you play but if you run&gun quickdraw, lightweight and dexterity are VERY important. It's also important to pick killstreaks you can achieve, turret is very useful in my opinion. I also use it to guard myself when I drop a care package because the maps are so small. With this tactic I get pretty good results most of the time.
e: very important: I only play hardcore, I am pretty sure this setup is less good in normal.