Most of the time I play Reach I'm in SWAT, but eventually I come out of my rut and jump into some Team/Squad Slayer.
All I can say is...grenades. Yeah I use them, but all I hear during games is the ***** sound of grenades. People seem to rely way too much on them. It's a small problem in Team Slayer, but it really annoys the heck out of me in Squad Slayer. I actually play Team Slayer over Squad because of Armor Lock.
No I'm not one of those people that goes into Armor Lock at every instance a bullet is shot, it's just a nice defense against storms of grenades.