High: some late night games with my non-BSN buddy WreckingChimp. Me as the Drell Adept with Venom, him as the Vorcha Soldier with Hurricane. Many biotic booms and fire explosions!
Low: Wave 10, Giant, vs. Reapers, Devices. I go to do a device in the raised control room area. There is a single Banshee there, while WreckingChimp entertains the rest of the Reaper posse elsewhere. "No problem," says me, "I shall Cobra Missile this Banshee from the safety of the ramp."
My missile sails directly through the floor and disappears. The Banshee teleports onto the same level of the ramp as me and immediately picks me up.
WTF!
High: However, earlier in that game I pulled off something amazing.
Wave 6, we're doing a hack at the bottom of the map.
Two Brutes are charging forward while WreckingChimp's Vorcha Soldier is Flamer'ing them.
Meanwhile I'm noticing we're being shot from the balcony near the ladder where a Marauder has taken cover.
I Reave the Marauder, then throw Cluster Grenades in the general direction of everyone.
Two 'nades hit the Brutes, setting off a fire explosion.
The third 'nade somehow finds the sliver in the balcony cover and hits the Marauder square in the face, setting off a biotic explosion.
It was the greatest Cluster Grenade throw I have ever made and likely will ever make. Sadly, there is no video.
(I tried "Xbox, record that" but my 360 only made grinding hard drive noises at me in response.)