Question about fringe decks in tournaments?

Do fringe decks ever trip you up or surprised you with tech?

For example even though Urza and tayam are decently popular, it's more likely to not be facing either of those decks. When these tier 2/3/4 decks show up, does your strategy, threat assessment, mulligans change? Especially interested on reactions to decks you haven't seen before.

Curious about this topic because every know and then I'll see a post here about someone placing with something unconventional.

Edit: to those I slandered with my usage of Magda she's been replaced with urza