Randomized surfing
Well, none of my efforts have been seen in use because I didn't release any of them. :-) But I've tinkered quite a bit, so it's not for lack of trying.
The idea I thought had the most promise involved generating a completely new/random movement profile every time you get hit. Also tried instead/also a new profile every X ticks, or every time a wave passes, or modeling those random stats in a fair number different distributions (flat with flat juice to super spiky), and in various mixes of random + normal flattener. I guess it's possible some of those would've helped against certain bots, but my testing on this is usually restricted to 2-3 strong bots, since the only improvement I'd really care about is beating DrussGT without sacrificing too much vs Shadow/XanderCat. ;)