Left 4 Dead 2 has two weapons that don’t fall into the basic tiers: the M60 and the Grenade Launcher. Both guns have counterparts in Payday:The Heist and it’s honestly more for the second game that I’m writing this article.
Let’s do the more obvious outlier first. The M79 Grenade Launcher is an oddity in both games; the only projectile weapon, the only explosive weapon and the only weapon almost impossible to main because it has severe ammo issues. It’s difficult to give recommendations on using it in Left 4 Dead 2 because it’s an unwieldy thing full of downsides. Your teammates won’t appreciate the massive amounts of friendly splash damage even controlled aiming can dole out, you won’t appreciate having no primary once the grenades run out, and the single-shot slow-reload can make it a real hamper to try and use in combat. I rarely consider it worth dropping my current weapon for.
It’s a far more useful weapon in Payday where it gets shunted to the secondary category (meaning you only sacrifice an SMG or pump shotgun) and can gain more ammunition from bags and ground pickups. In particular, it directly counters the Shield enemy, capable of punching right through his otherwise-invulnerable riot shield. The lack of friendly fire in that game doesn’t hurt either. I’d recommend toggling off the leaf sights upgrade once you’ve unlocked it; it’s never done anything for me but clog up my vision. Interestingly, the grenades can also destroy specific walls in the DLC maps, but it’s not clear if that was considered an upside; the heisters usually benefit from keeping avenues closed off.
Payday also expands heavily upon the “light machine gun” branch of weaponry, a category which specializes in extremely large clips of high-damage bullets that suffer from poor accuracy and handling. The Brenner 21 fills this niche well with 120 shots before reloading and a lack of the usual LMG downsides like reduced walking speed or awful recoil. It’s a must-have for teams attempting heists full of tight corridors like No Mercy. I originally didn’t like the Brenner until I read this forum post and learned its unique playstyle.
Left 4 Dead 2‘s M60 makes a token appearance in only a few campaigns, and it’s alright for the 150 bullets you get, but the AK-47 can fill a similar role and not burn itself out after only 17 seconds of continuous fire. Honestly, by the time you’ve progressed through a campaign to the point where M60s start spawning, you’ve probably already found your favorite gun and would like to keep it for the rest of the campaign.
I wish this could be the first time I mention TF2’s Mann vs. Machine without immediately stating that the chosen weapons are virtually unused, but there are no light machine guns in TF2 and I recently discovered that apparently pro MvM Demomen just equip the Booties for some free health and pour all their credits into their Stickybomb launchers. This makes me sad, but it just goes to show that MvM’s meta is very heavily built around buffing the crap out of your primary and then equipping utility secondaries that further buff the team’s primaries.