Large Language Models (LLMs) demonstrate impressive capabilities but exhibit inconsistent performance across diverse domains. We propose DFPE (Diverse Fingerprint Ensemble), a novel training-free method that systematically constructs subject-adaptive ensembles by balancing model diversity and competence. DFPE introduces three key innovations: (1) semantic fingerprinting using averaged response embeddings to capture distinct problem-solving patterns, (2) DBSCAN-based clustering with quantile-based competence filtering to ensure diverse yet capable model selection, and (3) exponentially-weighted aggregation adapted to subject-specific performance. Our method's effectiveness is highlighted on the challenging MMLU-pro benchmark, where DFPE achieves a striking 17.1 percentage point gain over the best single model, reaching 71.4\% accuracy. This strong performance is consistent across other standard benchmarks, with significant accuracy improvements of 4.4 points on AGIEval and 2.7 points on MMLU. Our results underscore that a systematic approach to ensemble construction - one that balances diversity, subject-specific competence, and adaptive weighting, can substantially enhance the generalization and robustness of LLMs on multifaceted language understanding tasks.