So many annoying mechanics (and ever increasing in number), so little time!
Any slot which, with almost deliberate glee, puts a “bonus” wild in a non affecting pointless location. Example: Moon Princess and clones. Actually almost any Play’nGo drop game.
Any game which charges increasing amounts to spin a single reel or similar. Slingo is exceptionally dodgy in this respect to be honest. It’s one thing to be able to do say £20 spins which you can control from the off but these actively encourage spending 5, 10, 20x your stake and upwards repeatedly.
Mystery symbols on Megaways slots which leave a gap on one of the first 3 reels then with a cast iron guarantee reveals a symbol not already on the screen. In fact I believe some are designed to do this so the minute you get a gap you know you are winning nada. That these now almost always are no more than 10x max makes the whole exercise tiresome.
I’ll throw my two penny’s worth in respect of teases as I have hated these ever since they were introduced and have commented on previously. Could never understand why someone thought it’d be a good idea to wind up someone who is often going to be irritated as they are losing by pretending to offer something then take it away. The fact early instances of this more often teased than bonused made this deplorable. I’m sure the designers got a good laugh out of it. Unfortunately pretty much all companies have this crap programming to one degree or another. Funnily enough Blueprint, the original instigator of this have tamed their teases down some what. Red Tiger, however took this to the max along with countless other annoying things all their slots seem to do.
And finally, not so much a specific mechanic, the “boy these slots are bloody boring when you don’t have the option to bonus buy” award! Yes, slots which do pretty much F all for hundreds of spins, sometimes thousands. Bonanza is still pretty much top of the pile but at least it’s base game is reasonably balanced. No, the slots which have a bonus hit around the 350-400+ bracket, then spit out 10-20x more often than not. Good job I’m not looking for fun while I lose.