The usual NaOH and HCl ones. I think I've done most of those correctly.
with HCl and H2
In+Methyl red. That one was horrible
the color change wasn't what I expected. A mess.
Iodine-in-cleaning-products titration with sulphite and starch. That was the best one. One drop changed the solution from pitch-black to transparent.
Boric acid and mannitol made a weird, monoprotic complex which removed all the fun. We even used H2
In again. No new reaction, no new indicator, no new colors. That could have been any other acid and we'd never have known.
Volhard and Mohr's. We all expected a blood red color for the end point because the procedure said that. Turns out the the end point has a faint orange color, not a blood red one. Mohr's was much friendlier.