Have you played Mann vs. Machine? If not: it’s basically a set of horde modes, where big mobs of enemies (robotic versions of the classes with different loadouts and some buffs) come at you. They carry a bomb, and you have to stop it from reaching your base. There are also giant versions of the enemies that have huge health (like a giant soldier who shoots rapid fire crit rockets in volleys of like ten).
What I like about it is that you can buy buffs for your character based on how much money your team collects during the waves (dropped by dead enemies). Like you absolutely need these enhancements or you won’t be able to finish the campaign). By the time you get to the last couple of rounds, if you’ve been collecting money properly, your character is like superman but the gameplay is so intense that you need that. Some characters get weird little enhancements too, like the Scout scoops up money from a much larger radius, and the money heals him, the Medic gets a big shield that’s bullet/rocket proof, and damages enemies if you touch them with it.
There are beginner modes (where the hordes are like a couple dozen scouts at once and maybe a lone giant at the end) to expert modes (where you really need to be coherent as a team to pull it off… giant Demomen covered by half a dozen Uber Medics are largely unstoppable unless you know what you’re doing). There are some other features, but going back to regular TF2 is… so slow and boring now?
If you’re down, I will probably be playing tonight. Mann vs Machine is free, but if you get into it, I’ll kick down a couple passes to Mann Up Mode (which is a set of slightly different maps, but if you pull them off, you get a shot at a cool gear at the end of a tour, and people there tend not to be farting around because they’ve all got a pass on the line).