These achievements were added in the "Love & War" Update.

Achievement	How to unlock
Air Raid	As a demo, kill 3 enemies in a single parachute deploy.
Back 2 Back	Using the Back Scatter, kill a heavy/medic pair within 20 seconds of each other.
Back in Business	Using the Back Scatter, kill 20 spies from behind.
Bombs Away!	Kill 3 enemies with the Air Strike in a single rocket jump.
Chain Reaction	Get 3 kills within 6 seconds using the demoman's charge.
Conga Line	Do the conga (taunt) with 10 or more players at once.
Dogfight	As a parachuting soldier, kill another parachuter.
Eagle Eye	Using "The Classic," kill a rocket/grenade jumper with a full-charge, no-scope headshot.
Emergency Brake	Kill a charging demoman.
Fast Fingers	Backstab a scout using the Back Scatter.
Flight Cancelled	Using "The Classic," kill 25 parachuting players with a critical headshot.
Flight Control	As a parachuting demo, kill another parachuter.
Flip-Kabob	Ignite a player who is being flipped by the Flippin' Awesome taunt.
Head-On Collision	Kill a charging demo while charging yourself.
Hipshot	Using "The Classic," kill 10 enemies with a full-charge, no-scope headshot.
Maximum Potential	Reach the Air Strike's maximum clip size.
May I Cut In, Too?	Kill 10 players doing the Square Dance taunt.
Nose Dive	Kill 10 players parachuting with the B.A.S.E. Jumper.
On the Rocks	With the rock-paper-scissors taunt, lose 3 times in a row while picking rock.
Operation High Dive	Parachute 19.47 miles as a demoman.
Party Crasher	Kill 3 players doing the conga within 5 seconds.
Prime Cuts	Using "The Classic," gib all 9 classes during a single round.
Project Excelsior	Parachute 19.47 miles as a soldier.
Punching Bag	Kill 10 snipers using The Classic.
Running With Scissors	With the rock-paper-scissors taunt, win 3 times in a row with scissors.
Severed Ties	Using the Back Scatter, kill 20 friends from behind.
Showboat	Do 10 partner taunts with a teammate while capturing a control point.
U-Turn	As a demo, kill a foe you couldn't see at the beginning of your charge.
Upper Hand	Kill 3 enemies during a single parachute deploy.