Units you hate to play against, but love using?

Morning folks.

On the drive into work this morning I was listening to 40KUK's latest podcast, specifically the section they have called "Operation: Codex" where this week they went through Tyranids.

Now, most of the comments were about the usual "competitive" list building for Tyranids, i.e. Tervigons, Swarmlord, The Doom of Malan'tai and Trygons which made me think about how I'm building my fledgling Tyranid force.

Not so much from the point of view that "I must have these to be competitive" but more "I really hate playing against these units, how can I be such a horrible person to force them on my opponents?".

For example, I've been playing a LOT of Chivalry: Medieval Warfare on Steam recently. For those who aren't aware of it, it's a "first person slasher" with Knights, Men at Arms, Archers, Trebuchets, Warhammers... the lot.

Now. In that game, the Archer class gets a lot of people annoyed, very quickly, especially if there's a lot of them on one team as it forces players to either have to all go as counter-Archers or swap to heavy Knights with large shields who are slow moving.

In a game that is based around a really ace melee combat system, there's nothing more irritating than getting sniped by a crossbow.... HOWEVER.... when you're playing as an Archer, it's immensely satisfying to be murdering people from afar with the bow.

I really enjoy playing as the Archer in the game, however, I find myself after a while starting to feel the frustration others may have when playing against me and a few other Archers on a team.

Which handily leads me into.....

What units in 40K do you HATE to play against, but what do you / would you use in your own lists?

Doom of Malan'tai

• This guy burned me so many times in 5th edition that I would get the red mist whenever he dropped in and forget the rest of the Nids and just attack him. 
• Flipside is, I can see the merits of using him in exactly that way. A persistent threat dropped behind enemy lines that can do damage in both player turns.

Tervigons

• Again, these guys are mega frustrating to play against. They're scoring (99% of the time), very tough, cast Psychic powers and can spawn more blokes who they can then buff up. Annoying yeah?
• From the Tyranid player point of view, these are invaluable objective holders / objective grabber spawners.

Nob Bikers

• Not so much nowadays, but in 4th and early 5th edition, these guys were everywhere and nigh unstoppable once tooled up. Warboss made them scoring, FNP on them, invulnerable save, cover save permanently, etc. etc.
• I used these guys in pretty much every main Ork list that I took for a few years until I started messing around with other styles of list (Trukk Boyz heavy, Kan Wall, etc.). I know how much they can annoy opponents at times when they'd pump everything into them and maybe 1 would fall down as a result.

Long Fangs

• These guys sit at the back of the board with heavy weapons (normally missiles), can split fire to hit more targets and can also handle themself quite well in close combat. Irritating yeah?
• I do the exact same thing (but usually twice as many) with my Imperial Guard heavy weapons teams. They're not as durable, but there's more of them and split into different squads. Everyone likes to have a backfield holding unit that can do some long-range fire.

Tau Battlesuits

• In 4th edition these used to absolutely infuriate me with their jump-shoot-jump shenanigans when they were present at a lot of events and used regularly. With the new Codex, this flea circus will be back again for more of the sorts.
• From my point of view though, they're like extremely mobile Terminators, I love the look of them floating around a force of Fire Warriors and they also look fun to paint.

Helldrakes

• These guys were the bane of my existence for the last few games and at our inter-club Tournament a few weeks ago. They'd smash up a flyer / unit, then over the top and Baleflamer another unit, hoovering stuff off the board.
• However, why would you not want a flying unit that can have a flamer that can fire 360, at distance, and sweep stuff off the board?

That's about all I can think of for now but what about you guys? What are some of the units in your armies that you like to use, but have played against them and found them horrible to deal with or give you the red mist?